Good play by Amazon. There is a lot of buzz around mCommerce right now - what is it? what does it mean? how fast will "it" grow? what role will it play in the multi-channel retail experience?
One of the top reasons consumers give for buying in a physical location after conducting research online is immediacy - can get it/buy it now. On a cell phone in a physical location, comparison pricing has the potential to either finalize the deal (if the store does indeed have the lowest price) or take the customer out the door - either to another store or online.
SnapTell - already popular with cell phone users - adds to Amazon's growing portfolio of mobile services (which I find impressive already) - and is a bit of a defensive move. I think they may yet bring a few people back to online (or one of their retail partners) with this service.