Yammer, a Twitter-like microblogging tool for businesses, won the top TechCrunch50 prize of $50,000, TechCrunch announced yesterday. I spoke with CEO David Sacks about the company after he presented on Monday, and he told me that it was "really cool" that judge "Marc Benioff said he liked it the best."

Benioff, the CEO of salesforce.com, said he would buy Yammer if it introduces an employee verification system, according to a report by TinyCrunch.

Sacks created Yammer internally for his other start-up company, Geni, and decided the product was so good he should let other companies use it. Employees will be able to use the service for free, but companies that want to have administrative control of their Yammer accounts will have to pay up.

Kelsey Blodget, Associate Producer