At The Motley Fool, we poke plenty of fun at Wall Street analysts and their endless cycle of upgrades, downgrades, and "initiating coverage at neutral." Today, we'll show you whether those bigwigs actually know what they're talking about. To help, we've enlisted Motley Fool CAPS to track the long-term performance of Wall Street's best and worst.

And speaking of the best ...
Last week, one of my favorite Fool writers, Travis Hoium, made the bold prediction that Clean Energy Fuels (Nasdaq: CLNE) was "ready to pop in 2012." Citing a whole host of tailwinds giving this stock a lift -- from the company's partnerships with Flying J to its $150 million capital infusion from Chesapeake Energy (NYSE: CHK) to the plummeting cost of natural gas that's made the fuel much more affordable for use in transportation -- Travis argued that while "the transition to natural gas will be slow ... Clean Energy Fuels looks to be one of the companies leading the way."

The question is: Which way is this road headed?

The best, and the rest
Yesterday, Clean Energy unveiled the first phase of a 150-LNG fueling station "American's Natural Gas Highway" project. By the end of this year, the company plans to have nearly half these stations up and running, pumping natural gas into tractor trailers in 33 states across the nation. Manufacturers are hurrying to build trucks capable of running on the fuel, too, with Navistar, Westport Innovations (Nasdaq: WPRT), and Cummins (NYSE: CMI) all on board already.

Yet despite the heavyweight support being thrown at this new trend in energy, Japanese banking powerhouse Mizuho announced yesterday that it was initiating coverage of Clean Energy at "underperform." Why?

Guessing game
No one's quite sure. So far, no major media outlets have details on the Mizuho sell rating. But I think we can take a guess.

Right now, Clean Energy is not a happy camper, profits-wise. The company's trading at meaningless P/E due to its booking negative profits for the past 12 months. Once the final results are in, Clean Energy is expected to lose as much as $0.54 per share for 2011, then post another loss this year. In fact, even the analysts who do like Clean Energy admit that it probably won't book its first full-year profit until 2014.

And it gets worse. Building 150 natural gas refueling stations is an admirable goal, but it won't come cheap. Already, capital spending by Clean Energy is running to nearly $60 million per year. Add in losses from operations, and the company tops out at $72.5 million in annual cash-burn. And this is a firm with no cash balance to its credit, a company actually in hock to the tune of $129 million net debt.

Foolish takeaway
That's a worrisome trend. Clean Energy may be at the forefront of a new revolution in how Americans fuel their cars and trucks, but if so, it's at the bleeding edge of the revolution. Building out a network of fuel stations is going to cost big bucks. It will necessitate Clean Energy either going deeper into hock to its creditors or, more likely, issuing additional shares to get hold of the cash it needs -- diluting existing share values in the process.

My guess: This is at least part of the reason that Mizuho predicts Clean Energy shares will fall as low as $10 over the next year.

And my advice? If a 25%+ decline in share price doesn't scare you -- if you think that's just a pothole on the highway to natural gas success -- go ahead and buy Clean Energy today. But if you don't think you can stomach the drop (and I, for one, could not), you're better off sitting on the sidelines for now. If Clean Energy makes a go of this, there will be plenty of time to buy the shares once it's proven the business model is viable. Given my druthers, I'd buy the stock after the drop, not before.