Interesting.
I buy from Amazon about as frequently as I do from ebay (once or twice a month, usually) and I've never noticed a discernible difference in shipping times from one or the other. Usually, though, if I'm getting something from Amazon, I'll look for a seller that offers free shipping if I order over $25 and just expect it to take awhile. Still, that's usually a week or so, which is reasonable for me. Most of the time when I sell something on ebay, I ship as cheap as possible, so I don't expect anyone else to do differently.