I'm sorry, American Express (NYSE:AXP). One buy doesn't turn you into a PayPal killer.

The financial services giant is paying $300 million for Revolution Money, the online payment platform spearheaded by former AOL whiz kid Steve Case. It may be a perfectly reasonable purchase for AmEx, but I had to laugh at the headlines that played this up as a serious threat to eBay's (NASDAQ:EBAY) PayPal.

Do we really need to go through a history lesson, here?

The dot-com graveyard is littered with companies that tried to take on PayPal. Yahoo!'s (NASDAQ:YHOO) PayDirect, Microsoft's (NASDAQ:MSFT) Passport, and Citigroup's (NYSE:C) C2it all faltered. Even eBay gave it a college try, teaming up with Wells Fargo (NYSE:WFC) to launch Billpoint. That was another flop, forcing eBay into acquiring PayPal to ride the gravy train that was facilitating many transactions on its auction site.

Revolution's MoneyExchange platform has potential, but bigger companies failed when PayPal was significantly smaller. No one is likely to catch it now.

Then again, maybe this deal isn't so much about making a dent in PayPal as it is for the name of self-preservation. A key component of MoneyExchange is the RevolutionCard credit card. Offering no interchange fees and a mere 0.5% transaction and settlement hit, Revolution has already landed a fast-growing list of merchants including Whole Foods Market (NASDAQ:WFMI). AmEx charges considerably more, so why can't this be a defensive purchase? If it sees Revolution bumping AmEx out of stores, it now has the power to twist the screws accordingly.

So kudos to AmEx for killing a disruptor while it was still in the crib. Slaying PayPal, however, is a different matter entirely.