When I buy shoes on Zappos, I am trusting an existing brand that I've worn before (I wear the Nike Pegasus running shoes; the 33 model is basically the same as the 31s that I have on my shelf) and I'm happy to buy them from Zappos instead of a retailer.
I'd buy bike components online at Nashbar or Performance because I know what I'm getting from Fuji or Shimano. And Nashbar has slowly inserted themselves into that trusted space as well. But Vanhawks? I don't trust that yet.
If I'm being completely honest I think this depends a bit on disposable income. The guy I knew who bought a Davidson way, way back, knew a guy who let him borrow one. He had a family and coughing up that much money took some thinking.
The confirmed bachelor with many bikes, on the other hand, would try to do his homework but ended up with several he didn't like. He'd just resell them and try again. But biking was his thing. I think his bikes were worth more than his furniture.
You know we're talking about a company that already failed with a mail order only business model, right?
I buy shoes online when I've already seen them. But have you ever owned a high end bike? The experience is a lot different for buying shoes (although if I were in the habit of buying $2000 shoes I might feel differently).
You don't usually buy another one, unless you broke the last one. You buy something new, or different.