I can't seem to find an answer here, I probly just overlooked it...If I export my private keys from my online wallet, will they be removed from my mobile as well?
Exporting private keys normally doesn't mean removing them, it means copying them into another wallet but also retaining the original (either as a backup or so both wallets can be used simultaneously). If you mean deleting the private keys, then yes, once the mobile app next syncs the keys will be removed from the mobile wallet as well.
I guess the question would be is the mobile just a synced extension of the online.
Yes the wallets are shared between both. Blockchain.info acts a bit like dropbox every device that connects using the same identifier can download the wallet, modify it and upload it again.
What I'm thinking is that I could export private keys from online wallet, and keep them in my mobile. This seems safe, minus user error like losing your phone.
Wallets are always synced online with blockchain wallets, the avoids the problem of loosing your phone. There are other mobile apps which keep only a local copy.
https://bitcointalk.org/index.php?topic=40264.msg490783#msg490783 is the main blockchain thread.