But Groupon is now a public company and what they've done isn't exactly normal (though LinkedIn did something similar...and of course yesterday the follow-on was announced):

Groupon floated a record-low percentage of its total outstanding shares among U.S. Internet companies, helping to stoke demand. Only 4.7 percent of the stock was made available to the public, based on the offering terms. That’s less than in any U.S. Internet company IPO of more $200 million since at least 2000, Bloomberg data show.

http://www.bloomberg.com/news/2011-11-03/groupon-said-to-rai...