I read all my gmail accounts using POP/SMTP in a real mail program, so I don't see any advertising anyway. Won't make a difference. Except if they try to figure out trends by actually keeping statistics on the content of e-mails going through their system.
Hmm, maybe that's the reason I need to start using encryption.
That, and to annoy the NSA of course. /RS 'M-x spook'