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.

Interested in more info about Groupon? Click here to add it to My Watchlist.

Fool contributor Anders Bylund holds no position in any of the companies mentioned. We Fools may not all hold the same opinion, but we all believe that considering a diverse range of insights makes us better investors. Check out Anders' holdings and bio, or follow him on Twitter and Google+. We have a disclosure policy.