Here is a way of making money without a single follower. Works for me. http://barryrodgers.com/twittermarketingbot/
Sponsored Tweets pays me $10/tweet, but I've not received a ton of offers even though I hit 40k followers recently. I wrote an article a few months ago explaining how I went from 0 to 40k followers (30k at the time?) in 8 months. It was a TON of clicking and it's paid money and driven traffic, but be ready to actually work for it - automated means can get your account shut down so easily. Here's the link: How I'm Getting More Hits - Twitter
my main account http://twitter.com/CrunchNow has about 42k followers and i make around $20.00 a week from ad revenue
The real trick is to not spam a bunch of affiliate links to your followers. Not only will they get upset, but twitter is likely to shut down your account. What you want to do is build trust. Provide useful, fun, or enjoyable content for your followers and then once in a while post an affiliate link to something you know your followers will like. If you do this correctly not only will your followers buy what you linked them to, but they will thank you for recommending something useful.
I use twitter mainly for promotion. Once in a while, I drop an amazon affiliate link. I've had a decent success with it.