Thanks, formol.
We've discussed it before, and we've certainly not ruled it out. We might give it a try in the near future.
My concern is that we don't always instantly know the answer to problems. Forums and email afford us the time to think things through, do testing on our shop machines, dig through logs, etc...
Forums also create an easily searchable record of fixes for customers and the community.
IRC may be a bit too instantaneous (and stressful?). It wouldn't be so difficult with easy answers. But easy answers account for a fairly small portion of what we do.
For the same reason, phone support can be tough too. But most people contact me via forums or email, so the phone support is manageable.