Okay, thinking a few years ahead now, when OS X Giraffe (Yeah, yeah it's not a cat I know but I like Giraffes!) comes out. How do you clean install that? Are you going to need to buy Snow Leopard, to install Lion, to install Giraffe?
I thought Apple was all about being at the pinnacle of simplicity. This just sounds like the engineers are a little, erm? Well. Simple?
Also, whilst I get the need to move away from physical media. This just doesn't seem to have been thought out very well. They should at the very least offer the ability to order Lion on a disc if you want. The same as a large number of online software providers do. Order your software for £99.99, and add an option back up disc for an extra £9.99.