I noticed an Amazon page had "log in to read the reviews". Not sure how widespread that is, but seems like a big deal if you can see item reviews w/o login
well you need to login to buy it anyway so it's not that much of a problem
IMDb does it, too.
Wait, what? I’m not sure I’ve ever used an online shop that didn’t allow you to buy things without registering, but then again I do most of my purchases in person and offline.