Marketing Startups Get Serious About Twitter -...
Rated • 2 reviews • advertising, pay per click, pay per tweet, twitter, tweet • internetnews.com
For starters, there's TweetROI, a service that pays influential Twitterers for spreading the good word about marketers' products and services. In keeping with the social media theme, the last bit of the company's name actually stands for "Return on Influence," not "Investment".

