If you've been sharing content with your Facebook friends or email contacts then you've probably seen the little green symbol from ShareThis, a young Cincinnati start-up that hopes to become the big name in online sharing. Much like Google 10 years ago, which dominated the world of Web searching, ShareThis, founded by Tim Schigel, wants to be the ubiquitous choice of Web surfers to share information from visited websites with their friends and contacts. The company has attracted $21 million in venture capital investment, and its service is used by more than 125,000 websites worldwide. More than 186 million people per month use the online button.