What if a fat person is trying to lose weight ? Ads have measured that this individual is likely to buy cake and present him with delicious assortiments everywhere he goes. It's beneficial for the companies but what about that individual ?
Conversely, what if the algorithms have decided that the person is a good lead for a local gym, and those ads push him or her into losing weight?
We're all influencing each other, constantly. In a way, banner ads and such are some of the most honest ways of going about it, since they're clearly delineated as such.
The algorithms can only be accurate to who you are, not what you want to become.
If aforementioned fat person searches for "weight loss" and Google starts showing ads for that, haven't the algorithms been accurate to what (s)he wants to become?