Because it always gets on the front page of Hacker News.

Famous for winning the vaporware award two years in a row, :p.

Because they were featured on TechCrunch Cribs http://techcrunch.com/2014/11/18/tc-cribs-famo-us-the-startu...

This question was answered by the Founder Steve at a meetup in London. https://www.youtube.com/watch?v=qkaU2cFbXyg&feature=youtu.be...

I'm guessing it's the best domain name the founders had already.