I guess you have to go where the people are, but man, I wouldn't want to outsource the knowledge base/forums for a major product to a different company. Seems like a valuable asset to give up.
So the trade off (going where the users are vs. the assets) doesn't seem that bad.
Note that I've never been in charge of a large product like this, so take my opinion with a grain of salt.
It's a shame that the SO community is constantly killing interesting and useful questions, just because "they don't match their format".
I agree that is baffling the way interesting questions are always getting quashed.
And IE, up to IE8, used to require a lot of workarounds, so pretty much the whole community has already turned to SO for debugging.