I've seen ads on my work machine for things I'd searched for at home. My work machine is signed into my work Google Apps account (and never my home account; though I have used that in another Chrome profile) and home my home account.

So, even if you're not connecting logged-out users, it seems to me that you might be connecting different logged-in users accounts.

I don't mind; I'd rather have targeted ads than not; though it does seem a bit creepy and often it's useless - I'm sick of seeing ads for stuff I already bought; you're losing cash there!