You have to reckon that it's easier/cheaper to start an online business than a "brick-n-mortar" one. In my opinion, the online businesses that fail do so because their owners are unealistic. The easier something can be done, the more people will try it.

As a webdesigner, I can't count the number of people who approached me telling me : "I want to start a dating site" or "I want to start an auction site" just because they saw the success of ebay and meetic. Part from that, they had strictly no clue.