As a person who does about 75% of my shopping on-line (not just bike stuff, everything, including business supplies) here is my perspective, for what it's worth.

First I don't buy the "support your local economy" arguments. To me that idea is out of step with current realities. I prefer to buy from a Canadian company when I can, but that's only a small preference and I order from the US all the time. (I also know that the line between Canadian/US corporations isn't always clear! McDonald's Canada is a Canadian company... HBC (Zellers, The Bay) meanwhile has significant US ownership).

As both a consumer and a business owner, I go to local businesses for services, and shop on-line for goods. When the goods combine a service - eg I need advice on a bike part plus I want to look at some, that's local too. I don't think that most businesses that primary sell goods will survive for much longer on the local level, and if I owned a store I would be moving to a service model ASAP.

As a consumer I research products a lot, and usually am very specific as to what I want. I seldom go out to buy a new video card or a new handlebar. Rather I know the specific model number, package, etc. that I want. It simply isn't possible for my to walk into my L{whatever}S and find that item on the shelf, and ordering it is a hassle even when possible. I certainly won't spend the day on the phone calling stores and asking, "Do you have model XYZ-123a in stock?"

I'm not saying small, local, and often independent retailers will die out. Rather, just like any other industrial or economic change in history, businesses will change and adapt or die. The need for services won't die out, the need to see/handle/try some types of products won't go away, neither will the need for professional advice. Retailers who adapt to this will do well.

As a photographer I offer both services and products. My industry was hit by the proliferation of "portrait studios" in malls, and now by digital photography. Many photographers have predictions of doom-and-gloom as they see print sales go down. What they are not seeing is the need for the services of a professional photographer, that need is still there. Its just the product (prints) that people are no longer willing to pay premium prices for.

I ordered most of my bike upgrades from Nashbar, got a few at MEC. For helmet advice I went to my LBS, and they are the ones who will fix things on the bike I can't do myself. That, IMO, will be the typical consumer model in the coming decades.