> I can often tell what my girlfriend has been browsing for from the ads I'm hit with, for instance, which is somewhat creepy.

I've had ads for medication that I'm prescribed, or could be prescribed, play on other people's devices when they use my network. It's likely targeted because I don't get ads for other types of prescriptions at all at home.

I'm also pretty sure of some of the medical conditions my friends and family have based on the ads I consistently see in their homes.