My daughter, whose interests don't have anything at all to do with my profession (which is no suprise to me!) just got gmail. One of her first e-mails was from me, sent from my business e-mail account. Since I buy adwords using the same domain, google associates my e-mail address with my work (in case you can't guess, control engineering). So on my e-mail she gets ads highly targeted to me. These are for highly technical, narrow niche products that I and a few other people would find interesting.
In other words, if Joe Blow at Acme Widgets, email@example.com, sends an e-mail to his relative, who cares nothing about widgets, the relative will get widget ads.
This doesn't seem like a reasonable basis for targeting.