Believe it or not, plenty of people (big and small, in business terms) will pay you to "like" their facebook page and/or "tweet" their products, services, brand, etc. This can be an excellent way to generate some extra money from home for something you're probably doing anyway. But beware... your friends and followers on these popular social networks didn't join just so that they can see advertisements every few minutes.
In order to make this idea work, without simply ticking off everyone who started following your timeline in the first place, you will have to continue to regularly and actively contribute genuine, useful content. Posting a few advertising tweets each day, or liking 10 different company or individual fan pages each day will be much more tolerable to your friends and followers if you're generally posting something more content-rich, fun, or socially interactive. This, in turn, will make your advertising tweet/likes far more valuable and effective for the people who were looking to pay you to do them!
There are a number of ways that you can find people who would be willing to pay you for this service, provided you have a strong following on one or more of these social networks.
1) Fiverr can actually be a fantastic place for you to throw up a gig to tweet a certain number of links to a certain number of followers, or guarantee a certain number of likes on Facebook, for a fee.
2) Sites like the one this link will take you to in a new window have listings from advertisers who are looking for someone who is willing to spend a certain amount of their social networking time on helping them get the word out about their products, services, programs, etc.
3) Joining a site like PaidPerTweet will allow people who are interested in hiring you to tweet their message/link find you. Sites like these can be rather competitive and there will be people who have a million or more followers that you're competing with, but their prices will also be more expensive than you're likely to charge for a single tweet to 1000 followers.
Social media marketing is huge right now. Marketers are realizing that this platform allows them to reach the largest, targeted audience possible without cutting so far into their profit margin that they may as well be giving the stuff away (which is what PPC has become for so many - but that's a different post). Regardless of experience or skill set, you too can take advantage of the social media marketing craze and leverage your pull in any/all the social networks you're a member of.
My take on it is this: I don't join social networks, or follow/befriend people just so that I can see advertisements, and I doubt you do either. But if my "friend" is posting a lot of fun and/or relevant content, I don't mind seeing an advertisement thrown my way now and then either. Ads are all over everything - the internet, the radio, TV, and so on. At least they aren't calling my house during dinner to try and get me to listen to their pitch! So go ahead, make a little money from the time you spend on Twitter or Facebook. Why not?