So, it turns out that eBay (NASDAQ:EBAY) does obey some of the laws of gravitation and valuation visited upon the rest of the universe.

Around the water cooler -- even here at Fool HQ, where we ought to know better -- there are a couple of refrains that support that common contention that eBay simply shouldn't be valued like a regular company.

One of those, the old "limitless growth potential" line, fell by the wayside a couple weeks back when the numbers showed that eBay can't continue its meteoric sales gains forever. The second argument, that eBay has nearly unlimited pricing power, falls by the wayside today.

Yesterday, eBay released a statement from President Bill Cobb that promised some old-school customer service. Next in line, a partial retrenchment in fees aimed at calming the storm. Apparently, boycotting eBay isn't exactly the same as boycotting air, as my Foolish colleague Rick Munarriz pointed out last month. True, the firm's moat is impressive, but that doesn't mean it can afford to do whatever it wants. I remember selling gear online before eBay, and I can certainly imagine going without.

I'm betting management can imagine a world where sellers look elsewhere and competitors creep up, even slowly. Otherwise, why recant on a portion of those recent fee increases?

The bottom line for investors is, do not just pay and pray. Even the most spectacular growers have their days of reckoning. And when they come, it's not pretty. Amazon (NASDAQ:AMZN) has been pretty bad for the overly optimistic over the past few months. Taser International (NASDAQ:TASR), Starbucks (NASDAQ:SBUX)? Different businesses, same story for shareholders who bought at the wrong time. If you have to have a chunk of hyper growth, you might as well wait for inevitable sale.

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At the time of publication, Seth Jayson didn't have positions in any firm mentioned. View his stock holdings and Fool profile here. Fool rules are here. Amazon and eBay are Motley Fool Stock Advisor picks. Taser is a Rule Breakers pick.