Solving Problems for For-Profit Companies

I'm sure I'm not the first to realize that I'm solving a problem for a for-profit company. Do forum rules or etiquette preclude suggesting that these people pay me for my services?
I like solving problems pro bono for hobbyists, but I get a little miffed when I realize that my time is being turned into dollars for someone else. Sure, I could just drop out of the thread, but I also hate to do that.

I hear ya... Me wonders if Microsoft did this very thing with the xclamp/overheating issues of the Xbox 360. (can you tell I'm bitter?).

I suppose you could ask for compensation, but as there are some who share their experience freely, even with people working for profit firms, you won't have much leverage. But of course, you could try to consult, something I've thought about, but then you're into marketing and salesmanship, something that would hold me back personally, as I have no talent for that. But I think sharing information is generally good for the technical community. If I ever find work again and need some assistance, I'll have no problem asking. Hopefully, I've built up some good karma from helping others.