I first wrote about Chipotle (NYSE: CMG) (NYSE: CMG-B) back in October. I argued that while Chipotle was a fantastic company with a future about as bright as Tiger Woods had when he was a young cub, the stratospheric valuations accounted for so much future success that investor returns wouldn't be as spicy as the restaurants' salsa.

Let me say it again: I think Chipotle the business is about as phenomenal as it gets. The brand recognition, the lines out the door, the addiction factor that keeps me coming back day after day -- it's all pretty impressive. It's Chipotle the stock that makes me quiver.

With a market capitalization of $3.88 billion, what exactly are you getting for a share of Chipotle stock? You're getting a slice of the company valued at nearly 44 times 2008 earnings estimates. Of course, Chipotle's growth is sure to be stellar, but you may want to take a second look at the price you're paying for success.

One of the most ironic aspects of the Chipotle craze -- one that you can't tell from looking at the company's financials -- is that there is a line out the door nearly every minute the restaurants are open. That said, it doesn't seem far-fetched to assume the majority of growth will come from opening more stores, similar to how uber-growth stories in the past, like Starbucks (Nasdaq: SBUX), have sustained high growth.

Management has expressed a target of opening between 130 and 140 stores in 2008, or an increase of about 20% over the roughly 670 restaurants now operational. Add in the double-digit comps the company has produced over the years, and it seems reasonable to me to place an expected earnings growth rate around 30% (which, mind you, is more than it grew in 2007).

Of course, 30% growth is nothing to sneeze at, but is it worth paying the sky-high expectations built into the stock price? Let's look at it this way: Average analyst estimates are for per-share earnings of $2.72 for all of 2008. Say 30% earnings growth is achieved for three years after that. Come 2012, you'd be looking at around $5.30 in per-share earnings, assuming some share dilution to finance growth.

By this time, 30% growth prospects will certainly start to become a stretch; there just aren't enough prime locations to continue the endless onslaught of burrito madness. While growth will continue for many years to come, a more reasonable P/E ratio will be in store to reflect reality. What that ratio will be is anyone's guess at this point. I can't see four years down the line any better than I can predict winning lotto numbers, but 25 times earnings -- comparable to that of other fast-food joints like Yum! Brands (NYSE: YUM) and McDonald's (NYSE: MCD) -- seems plausible. Oh heck, just to keep the naysayers away, I'll say the multiple four years out comes to 30 times earnings.

At a 30 P/E ratio and $5.30 in per-share earnings, Chipotle would fetch $160 four years out, leaving you with a gain of 6.7% per year had you purchased shares at today's price. I don't know about you, but that doesn't seem like much of a mouth-watering proposition to me.

None of that includes the possibility of interruptions down the road. A recession, an increase in food prices, increased competition ... being priced for perfection doesn't leave any wiggle room for the realities of business life.

Big investment gains are made before the masses pile in. While the growth party is far from over for this business, the lights of the shareholders' party may soon begin to flicker. It isn't simply growth we're after, it's growth at the right price. While Chipotle fills the former, the latter may well leave investors with an upset stomach.

Don't forget to read the rest of the Duel and vote on a winner.

Chipotle is a Rule Breakers recommendation and Chipotle B shares are a Motley Fool Hidden Gems recommendation. Starbucks is a Stock Advisor pick. Check out either service free for 30 days.

Fool contributor Morgan Housel doesn't own shares in any of the companies mentioned in this article. A special thanks goes to Chipotle for causing this article to take far too long to write, as thinking about its food forced him to take a steak-burrito break midway through. The Fool's disclosure policy is all about investors writing for investors.