Google does the same thing. So what? If I'm going to have to look at ads, I'd rather they be relevant. I've actually found Facebook ads genuinely useful on a few occasions. I even applied for a job that I heard about on a Facebook ad once. What I hate is when my friend uses my computer to search for tents, then all I see is tent ads all over the internet for the next month.
lol. I hear ya. (But I think Google and Facebook's data are qualitatively a bit different.)
It's anyone's guess whether this online privacy stuff really means anything to most people. Obviously Google, Facebook, et al. are hedging their bets that it's not a big deal.
As users we can only speak for ourselves. This is because we generally don't watch others, looking over their shoulder as they use a computer to see exactly what they do... which raises an interesting question: Does that imply that we are recognising some sort of right to privacy? A lot of effort goes into trying to figure out how others use a computer. But unless it's study of volunteers it's not done by just standing behind them and watching.