NEW YORK – Groupon, the company that pioneered online group discounts, saw its stock rise sharply in its public debut Friday, showing strong demand for an Internet company whose business model is considered unsustainable by some analysts.

Groupon’s stock jumped $8.30, or more than 40 percent, to $28.30 Friday afternoon after earlier trading as high as $31.14. Big fluctuations are common for freshly public companies, and Groupon’s first-day rise was largely expected.

Still, analysts said this doesn’t ease worries about the risks concerning the company – especially as the stock price increases.

“Until investors see the full profit model unfold over time, expect this stock to be highly volatile with increasing risk as the market cap rises,” said Kathleen Shelton Smith, principal of Renaissance Capital, which operates IPOhome.com. “The first day of trading is typically more about supply and demand. Fundamentals will take over in the long run.”

Groupon has faced scrutiny about its high marketing expenses, enormous employee base and even the way it accounted for revenue until an SEC inquiry prompted a restatement.