[penguinvondoom]

The problem is that there are a loooot of ethical implication on using your own personal data in the first place, where that goes, who has access to it, how is it handled, and so on and so on. Then advertisements isn't anything but propaganda, which has its own set of implications. And then finally we have the ever present pressure to push more and more ads, thereby making the internet in general worse and worse, so the very field of ads is in itself unethical, as it is destroying the virtual environments we are building.

Also ads != recommendations. In a sense after a while these two are also at odds with each other. Cause there is again, the ever present need to sell you more stuff.