There may be some loss in the questions column, but probably not so much. As it is, irc exists and so does SO (and obviously there are other ways to get help beyond those two).

I still use both irc and SO, but for different things. I tend to go to SO if I have a specific question, but it's relatively contained, concrete and non-trivial. If I have a smaller question and Google fails me, I'll pop into irc and try there. If the question is larger (needs more setup to ask, for example), I go to SO first. At the same time, if the question is very open-ended I go to irc, since I find SO can somewhat unwelcoming towards open-ended, vaguer questions. (As an example of that, I'm working on a cli grading program in Ruby, and I'm having a hard time deciding the big questions: what goes where, which things are classes, how to store, extract and calculate the data. I spent about half an hour last weekend in irc with some random stranger who was kind enough to bounce ideas around. irc can also sometimes suck for vague questions, but sometimes it works.)

Good point, I still see a ton of questions on SO like, "How do I add two numbers in teh PHP?", which seem to get both upvoted and replied to a lot because hey it's easy karma. Chat is the perfect place for this kind of stuff, because a) most new programmers I would hazard don't know about IRC, b) you can help clarify a poorly or sparsely worded question quickly in chat and c) it will hopefully decrease the dross on the front page.

And another nice thing is that if you're in chat and a question is just too big or too detailed (or you just don't want to deal with it) you can always just tell the person "go post this question."

I think this would reduce a lot of the drive-by chat noise.

SO is kind of unwelcoming to that sort of thing, but the format of SO is just not well-suited to open-ended questions, or anything requiring more than a few words of discussion. The limits on replies and unpredictable order of answers make it frustrating.

Not to knock chat, but most of the questions I ask during the work week are answered within 5-10 minutes. It's only on weekends when I notice the turnaround is longer.