Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of online deal wrangler Groupon (Nasdaq: GRPN), still smelling of fresh ink, fell as much as 16% in fairly heavy morning trading.

So what: Groupon shares skyrocketed from the $20 IPO price to more than $28 on opening day, and have been in decline ever since. When the $20 IPO level was breached last night, investors got over a psychological barrier and accelerated their selling some more.

Now what: We're still nearly two months away from Groupon's first quarterly report as a public company, wherein we'll learn a lot about management's mettle and the long-term success (or lack thereof) of its coupon-printing strategy. Until then, I simply don't understand how Groupon hopes to ever make a profit without scaring off those crucial retail partners -- I wouldn't buy this stock at any price. Fellow Fool Jeremy Phillips thinks that LinkedIn (Nasdaq: LNKD) takes top honors for best tech IPO in 2011; me, I'd rather take a second look at Pandora Media (NYSE: P). None of these stocks are fit for the faint of heart, though.

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