I'm a coder, and there's still a lot of companies using crappy web forum software.
Why run a forum when you could point customers to StackOverflow, and have your tech support guys lurk there to help them?
Reasons I see it would be advantageous:
- don't need to host a forum (less bandwidth, server usage)
- better answers as there's less duplication, and bounties for unanswered questions
- but most importantly, people like me look at the number of questions/answers on StackOverflow to see if a new product is worth pursuing or not.
Full disclosure: I am not affiliated w SO, but I am a fan and regular user.
As has Facebook: https://developers.facebook.com/blog/post/545/
And perhaps others; these are not one-offs, StackOverflow has a policy of setting up these kinds of relationships.