Founded: March 2009
Launched: December 2009
Fun Fact: A total of nine people run the company.
Why FB Should Buy It: The social curation site lets users create a virtual "tree" that houses all discovered, organized, and shared info based on a particular topic, making it entirely visible on one screen. Even friends and unknown bloggers can add content to your tree. Facebook wants users to funnel all their content through its pages, and Pearltree could help them on the organizational tip—letting FB further infiltrate your non-Facebook web surfing.