It's not the ads themselves so much as the tracking required to target them. When it was just Google showing ads at the top of the search results that matched whatever I just searched for, that was fine and often even helpful.

When Google is tracking where I'm going, my browsing habits, and even where I shop and what I buy, that's when I start to get creeped out about how much they know about me.

If NBC was watching my TV and putting in ads based on every show I've ever watched, I'd be concerned about that, too.