It’s too bad that Dropbox isn’t a publicly traded company, because it would be a great time to buy its shares now that Microsoft (MSFT) CEO Steve Ballmer has given it his patented reverse-kiss-of-death. Ballmer, who previously predicted the iPhone would flop because it lacked a physical keyboard and that Android would fail because Google wasn’t slapping OEMs with any licensing fees to use it, told BusinessWeek on Tuesday that the cloud storage company was just a “little startup” that posed no threat to Microsoft’s own SkyDrive cloud service.

When BusinessWeek’s interviewer pointed out that Dropbox had 100 million users, Ballmer said that most of those users were consumers rather than business customers, which would limit the company’s revenue potential going forward.

“If you want to get numbers like 100 million, it helps to start with consumers as opposed to businesses so you’re doing an apples-to-apples comparison,” Ballmer said. “In general, I would say a much higher percentage of our unit engagement with our customers comes from the consumer. And a much higher percentage of our revenue participation comes from our business customers.”