Shares of Chipotle Mexican Grill (CMG) are falling more than 90 dollars today after reporting second quarter earnings last night. Revenue rose 21%, with earnings soaring 61%, beating estimates of $2.30 per share by an impressive 26 cents. However, light sales figures (same store sales of 8% versus expectations of double digits) are causing a huge sell-off today. This is a perfect example of what can go wrong when investors rush into stocks that are very expensive relative to their overall profitability. Any hiccup results in a violent decline. And this really isn't a hiccup except relative to lofty expectations. If you simply read the press release and ignored the analyst estimates, you would conclude the company is absolutely printing money at its restaurants. Unit-level margins approaching 30% are pretty much unheard of in the industry.

The problem is that prior to today's drop, CMG stock traded for a stunning 59 times trailing earnings. Even using this year's projections gets you to a P/E of 45x, more than 3x the S&P 500 multiple. Even a meaningful earnings beat can't help investors with the bar set so high. Today could very well be a buying opportunity if one believes in the long term growth story at CMG, however, with the P/E still sitting around 34 on 2012 earnings, it is definitely not cheap enough for value investors to get interested.

Full Disclosure: No position in CMG at the time of writing, but positions may change at any time