Yes, and likewise you don't have any guarantee that anyone you talk to, tell stuff, share stuff with, etc. won't go then share that with someone/thing you disapprove of. If that's really an issue for you, then just encrypt all conversations you care about, and don't talk to people you can't trust (and can't trust to use 'secure' methods, for however you define the term secure).
This is not a problem with GMail, per se. It's a broader issue of trust.
The difference is the concentration of email in one company's hands. Ironically it would be less of an issue if all my friends were using different providers but, since they're all on GMail, our conversations get sieved either way.
This is not a problem with GMail, per se. It's a broader issue of trust.