Want people to see your new site? Trying to promote your Fiverr gig? I can get any message you want, including 1 URL, retweeted by 500 people for $5.
Ever since the introduction of Google+, Google has been placing bigger and bigger importance on social signals when it comes to a given site's ranking in the SERPs. When people tweet with your URL, it looks like your site is becoming popular or even going viral!
No porn/pharma/gambling please.