This article assumes that the primary goal of the acquisition is the technology. Without having looked at the technology or commenting on its merits, I can think of a boatload of other things Yahoo is buying with its money:

1) Free positive publicity--publicity that doesn't constantly remind people how Yahoo! is circling the train; 2) The recruiting hook of "yeah, we're not stodgy anymore, we paid some kid $30 million!" which will fly with some people; 3) A new engineer who obviously has both technical and business skills; 4) A subliminal "don't forget, there's more of you turning 18 every day" to the rest of the organization.