I do buy almost anything online but shoes is probably the riskiest since fitting might not be always right. I do buy my running shoes online but I know the brand, model and size so it is a pretty safe choice.
I was looking on buying a new pair of Newtons which are not available on retail stores around here. Fitting would be an issue and returning the shoes is a pain, until I found out about Shoefitr which takes the guesswork out of online shoe shopping.
Shoes are scanned in 3D and will show you how they fit and compare to other models you might have tried or own.
What a great idea and service!