Edit: REALLY tired of all the idiotic downvoting lately. What I've said is factual. Don't be such a lazy fuck and post a rebuttal if you disagree.
This is not a problem with GMail, per se. It's a broader issue of trust.
If I continue to use Gmail beyond another week or two (what's that deadline, again?) I've implicitly consented to Google's policy on what they're permitted to do with my email. (One nice thing about Google: I can't really claim they haven't told me about this nonsense. They are taking the notification of their customers very seriously.)
If, however, I'm not actually a Google user, but the Googlers secretly reassemble my mailboxes by sniffing the inboxes and outboxes of all of my friends and relations... well, that's a bigger transgression. They didn't ask my permission to do that, and when they asked my permission to do similar things I said no. So they'd better be good at keeping their activities secret, because if I ever learn that they did it I'll squawk a long, loud squawk.
Sure, social disapproval doesn't have the force of law. (At least, not right away.) But it does have force.
But in practice I'm not sure how much this accomplishes.