The best way to deal with the vanity punctuation is as The Register do.
Note "Related stories."
Edit (as requested) a sample of headlines from online newspaper The Register: Yahoo! wonks!
brace!
for!
lay-offs!
Yahoo! buys!
TV-sharing!
startup!
IntoNow!
Yahoo!
Buzz!
Given!
Mercy!
Bullet! Yahoo!
to!
offload!
Delicious!
as!
early!
as!
next!
week!
Yahoo! revenues!
dip!
4!
per! cent!
You get the idea.
Yahooexclamationmark's PR boss may feel a bit ambivalent.
english.stackexchange.com/users/2614/RedGrittyBrick
It seems optional, considering that even business article talk about Yahoo, while introducing some facts at the end about "Yahoo!".
If your article is about the public corporation, you should use consistently one convention, preferably the one using the exact name of the company: "Yahoo!".
But "Yahoo" is also natural since: you won't find any punctuation in the host names: www.yahoo.com , not www.yahoo!.com at least, it won't wreak havoc in your word processor spell checker ;)
See Ignoring Punctuation in Names if you still have to use the ' ! '.
english.stackexchange.com/users/110/VonC
Some sites, will use Yahoo! while talking about the company, but others do not.
For example, check this CNN Money page that refers to the company as Yahoo!
Inc.
english.stackexchange.com/users/2329/kzh
From a legal standpoint, you want to use the the official trademark name that the company uses in naming itself.
Check court documents to see what Yahoo prefers and use that.
english.stackexchange.com/users/2578/S Red
Certainly you should use the name as the company prefers it, but there's nothing to stop you mocking it gently.
If I am writing to somebody at one of those 'cool' companies that disdain capital letters and spaces, I make a point of addressing the envelope to 'johnrsmith, coolconsultancy': similar use of exclamation marks seems only fair to Yahoo!
Incidentally, there is a village in Devon called Westward Ho!; the punctuation is undoubtedly part of the name there.
english.stackexchange.com/users/8019/Tim Lymington
Certain brands, such as  Yahoo! , insist that the exclamation is part of their name. In writing about such a brand or company, is the inclusion of the vanity punctuation right, wrong, or optional?  I would like my writing to be correct; however, of more concern with the average reader, I wouldn't want my writing to seem to be pandering.
How to handle a name that includes an exclamation point (or other punctuation)?
english.stackexchange.com
<punctuation><writing><proper-nouns>
english.stackexchange.com/questions/6114
english.stackexchange.com/users/602/Nicole
The answer to this question will be subjective and use of punctuation in brand names may be optional. However, some people would recommend finding out what the company prefers and using that. Use "The Register" to check the official format. How the Company is represented by third parties on websites can vary; some using the exclamation mark, some not. Legally, it would be preferable to use the Company's trademark as it is registered or use the forma the Company uses itself.
The answer to this question will be subjective and use of punctuation in brand names may be optional. However, some people would recommend finding out what the company prefers and using that. It seems optional as some sites, will use  Yahoo!  while talking about the company, but others do not. Also you won't find any punctuation in the host names:  www.yahoo.com , not  www.yahoo!.com  at least. But from a legal standpoint, you want to use the the official trademark name that the company uses in naming itself.
The exclamation point in "Yahoo!" may be seen to be optional. However, if your article is about the public corporation, you should use  consistently  one convention, preferably the one using the exact name of the company: "Yahoo!".  From a legal standpoint, the legal trademark version should be used. The answer to this question will be subjective and use of punctuation in brand names may be optional. However, some people would recommend finding out what the company prefers and using that.
Use "The Register" to check punctuation. Some websites add the exclamation mark to Yahoo, but some don't. It can vary. Legally, it would be better to use the Company's registered trademark. The name the Company prefers itself, should be used.
It seems optional as some sites, will use  Yahoo!  while talking about the company, but others do not. Also you won't find any punctuation in the host names:  www.yahoo.com , not  www.yahoo!.com  at least. But from a legal standpoint, you want to use the the official trademark name that the company uses in naming itself.
The answer to this question will be subjective, however, the use of punctuation may be optional. Some people would recommend identifying what the company itself prefers and using that.