I always see people advertising or promoting their businesses at Facebook and Twitter, which i think is really a good way to let people know about your business. Instead of paying for advertisement which is ridicously expensive, Facebook and Twitter are Free! That is a smart idea but just don't overdo it because it becomes so annoying to your friends when all they read on your wall posts are ads, ads and ads! We have to do everything in moderation, you know. I see just about everything at Facebook and Twitter now that i won't be surprised if one day, they start collecting fees from members which i hope won't happen.