Giffgaff, a UK provider of mobile phone services, has extensive user provided support in their forums.

If someone gives a useful answer you give them "kudos", and that translates to tiny amounts of credit on their bill.

It's likely that companies might want to offload the forums to someone like Imzy.

I suppose with Reddit's "flair" options you could put a BTC address next to your username in a lot of subreddits. But BTC is a lot more effort than just clicking a button, unless the site sets itself up specifically to use BTC, at which point why not just use real money?

Take a look at all the "gilded" posts on Reddit. I see dozens of them every day. People love spending a few bucks here and there to show their appreciation for good content, but all of that money goes straight to Reddit rather than the person that created or shared that content. I would much prefer the majority of my "gildings" to go to the user, rather than the site.

The vast majority of internet users are not and will continue to not be bitcoin-savvy for a long time.