For me, informed consent is the issue here. If I sign up for your website and then log in, I think it's probably fair game to target things to them. In fact,

For me, informed consent is the issue here. If I sign up for your website and then log in, I think it's probably fair game to target things to them. In fact, that's generally the point. My real world analogy is an invisible store employee following you around, helping you shop, but also writing down every movement you make, and every conversation you have. It's more than a little creepy if they do it without asking.