Multiple Accounts
I admire all the helpful tips and cynicism on offer, but I don't see what the point is for some of the comments advocating the use of multiple Google accounts...
If you log into them from the same place, surely Google are clever enough to associate information from different accounts to the same IP addresses? Even if the account user isn't guaranteed to be the same person, they're part of the same 'household', and therefore a correlation exists that's probably strong enough to allow targeted marketing?