I would be interested to know the advantages of this compared to working on a file in a shared git or svn depository?
The other advantage is the ease of collaboration. While there are plenty of people in the LaTeX world who know git, there are plenty that don't as well. ShareLaTeX gives everyone a point and click way to make sure they are in sync with their collaborators. That said, we're getting quite close to offering git access to the projects for people who want it.
Also, my apologies that we keep appearing on the front page (along with a few other similar sites). We're flattered that people keep submitting us though.