This is a difficult question, because English is in the middle of a shift of social mores with regards to obscenities and vulgarities.
The "traditional" swear words (fuck, shit, ass, damn, etc.) have had their offensiveness gradually worn down over the past century, to the point where in many communities they're generic modifiers.
Large parts of the Internet hold to this ethos.
However, this shift is by no means complete or universal, as many people will still be offended by those words.
Be very careful in unfamiliar situations with people you don't know, since you cannot easily predict how they'll react to your language.
At the same time, new language taboos are arising with regards to racial and some sexual epithets.
You probably would not see an economics blog use the word "nigger" so casually, nor "fag", "cunt", or others.
However, the social conventions regarding these are even more chaotic and context-sensitive than the conventions for the older expletives.
If you want to avoid giving offense, you should always stick to the most conservative, expletive-free register, as no one is going to be scandalized by your failure to say "fuck".
english.stackexchange.com/users/48/JSBձոգչ
Relative to where and who?
I wouldn't use the f word as a synonym for "very" in Salt Lake City, Utah.
In the Marines it's just another word.
Cusswords are interesting neurologically, they appear to be managed by a different part of the brain than the part that is in charge of ordinary speech.
So if the f-word really did become an ordinary word, (I think the Proto-Indo-European word was something mundane like "to strike"), it would need to be replaced by some other word.
More likely, a taboo word would disappear from use than convert to the stock of ordinary words.
Seeing the F word on the internet probably doesn't mean it is acceptable, the internet is the lawless wild west.
english.stackexchange.com/users/6/MatthewMartin
Depending on the circumstances and the company it varies between shocking (my Bridge Club) and background noise (the Steelworks), a former colleague of mine being the record holder for the most uses in one sentence (21).
See also Field-Marshal Slim's quotation of his driver reporting that the car was unserviceable...
"The fucking fucker's fucked."
english.stackexchange.com/users/305/Brian Hooper
There is good evidence that "bad language" is stored in a separate part of the brain:
witness the case of the deaf man with Tourettes syndrome who swears in ASL .
And swear words in foreign languages don't set off the same triggers in the brain, so it's very hard to judge how bad they are in context.
Foreign language learners should generally avoid swearing until someone else has done so first.
That's my advice.
The actual question, How bad is the F-word?
has a very context-dependent answer.
english.stackexchange.com/users/1696/TRiG
It seems that the FCC's 7-dirty-word rule has recently been overturned in some degree, a sign of the times: Jul 22nd, 2010 NEW YORK CITY—Noting that, "we face a media landscape that would have been almost unrecognizable in 1978," the Second Circuit U.S. Court of Appeals has struck down attempts by the Federal Communications Commission (FCC) to regulate so-called "fleeting expletives" in radio and TV broadcasts... read article (warning: expletive ahead)
english.stackexchange.com/users/30/Edward Tanguay
It used to be very bad, and because of this it has been overused lately, eroding it's superlative offensive status.
english.stackexchange.com/users/794/Humphrey Bogart
In British English as other answers have stated, it mostly depends on context; I would not use the word in front of my mother, for instance.
However it also depends on how it is used.
If for instance I saw something shocking such as a road accident and said “Fucking Hell!”
, few people would be offended.
But if I used it at someone, such as saying “Fuck you”, I would be being very offensive indeed.
english.stackexchange.com/users/26339/john
I am confused: on the one hand, many of my native-speaker friends keep telling me that the f-word is very, very bad. Much worse than the s-word for example. On the other hand, I see it being used everywhere; for example, in the blogosphere, even by respectable economic blogs (e.g.  http://www.zerohedge.com/article/guest-post-fuck-deficit-or-will-deficit-end-fucking-us ).  Is the former intensity of the word decreasing? Is its usage becoming more acceptable in everyday language?
How bad is the f-word, really?
english.stackexchange.com
<slang><offensive-language>
english.stackexchange.com/questions/406
english.stackexchange.com/users/43/vonjd
The answer to this question is highly subjective, and it may be the case that traditional swear words have become less offensive over time. In reality, how offensive or used the word is probably depends on context, region and how it's used. Views vary but take care not to use such language with people you do not know.
The answer to this question is highly subjective, and it may be the case that traditional swear words have become less offensive over time. In reality, how offensive or used the word is probably depends on context, region and how it's used. A lot of traditional swear words have had their offensiveness gradually worn down over the past century, to the point where in many communities they're generic modifiers. However, this shift is by no means complete or universal, as many people will still be offended by those words. You should be very  careful in unfamiliar situations with people you don't know, since you cannot easily predict how they'll react to your language.  If you want to avoid giving offense, you should always stick to the most conservative, expletive-free register, as no one is going to be scandalized by your failure to say "fuck". Also seeing the F word on the internet probably doesn't mean it is acceptable, the internet is the lawless wild west. In the end, it all depends on context.
"Traditional" swear words (fuck, shit, ass, damn, etc.) have had their offensiveness gradually worn down over the past century, to the point where in many communities they're generic modifiers. However, this very much depends on context. For example, it may be shocking at a bridge club, and quite normal in a steelworks. The answer to this question will be highly subjective and will depend on both context and whom you are talking to. However, it is claimed that swear words are losing their offensive status gradually.
A change in attitudes is taking place at the moment but to be on the side take care not to use such language with people you do not know. It depends entirely on who you are with - some people would be deeply offended but others would not care. The fact that it's on the internet widely means nothing.
A lot of traditional swear words have had their offensiveness gradually worn down over the past century, to the point where in many communities they're generic modifiers. However, this shift is by no means complete or universal, as many people will still be offended by those words. You should be very  careful in unfamiliar situations with people you don't know, since you cannot easily predict how they'll react to your language.  If you want to avoid giving offense, you should always stick to the most conservative, expletive-free register, as no one is going to be scandalized by your failure to say "fuck". Also seeing the F word on the internet probably doesn't mean it is acceptable, the internet is the lawless wild west. In addition, swear words in foreign languages don't set off the same triggers in the brain, so it's very hard to judge how bad they are in context. Context is important. You may not use the word in front of your mother, for instance but would use as an exclamation at something shocking.
It is claimed that offensive words are losing their offensive status gradually. The answer to this question will really depend on context and who you are talking to.