Yo! App

It took eight hours to build, and it sends the word "yo" to anyone you want on your phone, for free. Oh yeah, and it's already raised $1 million.

In what is sure to spark more talk of a tech bubble, Think Progress has a report on the Yo app, which does exactly what it says, and nothing else. Launched on April 1 (it was initially rejected by Apple), the app--created by Israeli native Or Arbel--is already drawing plenty of users, and an avalanche of snark. It took off when tech evangelist Robert Scoble called it "the stupidest but most addicting app ever." Thus far, it has attracted over 50,000 users, who have sent about 4 million "yos."

