It is important to me that whoever I work for is not actively working in opposition to things that I consider important. For me, privacy is one of those things. If I were working for a company that I felt was abusive in terms of privacy, I would absolutely quit (although I probably wouldn't have taken the job in the first place).

There's a tradeoff here, though. Just as it's hard to find another person who agrees with you on every issue, it's going to be hard to find an employer that isn't doing something that you object to. So, I'd say this is a "pick your battles" sort of situation. Know what your hard lines are and be inflexible about those.

For everything else, take a look at the bigger picture. If the good outweighs the bad, then don't quit.