I think I understand what you are trying to say -- that the wiki is a bad technology solution to the problem. Its because the wiki isn't where the decisions are happening.
However, in most small businesses (and lets face it, theres more SMB then there is large or enterprise customers hands down) the decisions aren't made on a wiki, or even e-mail for that matter. In a company size of 60-70 or less its still way easier just to walk over to their desk and talk it out. Who remembers hearing a conversation ending with "don't forget to put this on the wiki?" This sentiment being true in my own workplace, the wiki is still considered the de-facto documentation on a subject (guess how many pages are up-to-date).
I believe any successful business collaboration tool will fully grasp facilitating interaction in a way that meetings or quick one-on-one's can't. Having technology outpace human interaction when it is humans that ultimately have to fully articulate themselves I think is the largest obstacle.
TL;DR - I think I agree with you, but the real solution is still difficult to solve with technology alone.