Prescriptively, you're correct, this should be were since this is being expressed with the subjunctive mood.
Descriptively, I think you'll find both in the wild.
In informal speech, most people I know would prefer was in this case (and those that don't are sticklers for the subjunctive).
I do think that you are much more likely to see were written though, especially in formal writing.
Either form is correct, and the subjunctive forms are far from dead.
A more interesting question, I think, is whether or not the subjunctive mood is still being used and if the two forms have simply collapsed together.
Is this a meaningful distinction?
How could this be tested?
english.stackexchange.com/users/89/Charlie
"WERE" because it is the past subjunctive of "to be".
It's an oversight by the copy-editor.
It's not the biggest deal in the world since the verb "to be" is the only verb in Modern English wherein the difference is obvious, although, if one WANT to speak very formal, correct English, stick with the subjunctive.
english.stackexchange.com/users/2763/Nick
Not a native speaker, but indeed it is a conditional and therefore "were" should be used.
However, I hear the incorrect form more often than the correct one, so I guess that "was" is a colloquial, albeit grammatically incorrect form.
english.stackexchange.com/users/1100/Stefano Borini
I think we need only look at the copy-editor of this book's.
Who the hell allowed "was" to be put there instead of "were"?
I noticed it right away.
"What if there were a stack overflow on..." because it is not true.
It's a condition that is contrary-to-fact.
If it were talking about something true that had occurred in the past, then "was" would be appropriate, but the "what if" automatically triggers a condition
so it's in definite need of the subjunctive.
Probably the biggest problem with the "were" past subjunctive form is the fact that its present form is "be", but most people don't say it that way.
"What if there be a stack overflow on..." is the stiffly formal way of stating something that is possible but unknown.
Most people in modern English would replace it with "is" nowadays, but we still say "if truth be told", "whether it be", "if need be" and so on.
english.stackexchange.com/users/None/
Since that's proposing a hypothetical situation, yes it should be were .
english.stackexchange.com/users/1101/Bill the Lizard
"Was" is the indicative, "were" is a subjunctive.
Since it's a hypothetical, it should properly be "were".
But the subjunctive is effectively deprecated in English, so I expect that "was" is perfectly acceptable.
english.stackexchange.com/users/879/Seamus
Possible Duplicate: “If I was” or “If I were”. Which is more common, and which is correct?  Is this correct grammar? What if there was a Stack Overflow on… Shouldn't it be "what if there were a Stack Overflow on…"?
Which is correct: "what if there was" or "what if there were"?
english.stackexchange.com
<grammaticality><subjunctive-mood>
english.stackexchange.com/questions/2705
english.stackexchange.com/users/371/jjnguy
It is generally agreed that the correct form in this example would be "were" and not "was", and you are probably more likely to see "were" in formal writing. However, "was" is much more common in informal speech. You are right but both forms exist in real life and "was" is probably more common in everyday usage.
It is generally agreed that the correct form in this example would be "were" and not "was", and you are probably more likely to see "were" in formal writing. However, "was" is much more common in informal speech. This is a conditional and therefore "were" should be used. "Was" is colloquial, albeit grammatically incorrect.
As this is a hypothetical situation, yes it should be "were" as this requires the subjunctive. However, I hear the incorrect form more often than the correct one, so I guess that "was" is a colloquial, albeit grammatically incorrect form.  Either form is correct, and the subjunctive forms are far from dead. It is likely that both forms are found in common usage. However, "were" would be the correct choice in this context since the phrase takes the subjunctive mood. "Was" is used colloquially and is perfectly acceptable.
You are right but both forms exist in real life. It's incorrect but actually more widely used nowadays.
This is a conditional and therefore "were" should be used. Both forms are used. "Was" is colloquial, albeit grammatically incorrect. Since it's a hypothetical, it should properly be "were".
It is generally agreed that "were" should be used in this example because it takes the subjunctive mood. "Was" is used colloquially in this context and is likely to be acceptable. It is probable that both forms are found in common usage.