Personally, I don't like the idea of needing to give any of these Dapps continual posting permission. As an option, I'd be fine with it, provided I also had the option to give permission on a post-by-post basis.

That's basically how it works with Peakd.com and the Hive Keychain app. Each time you post or vote, Keychain creates a blockchain operation on your local machine, and then signs it with your private posting key that is stored in the browser (encrypted). Then the signed transaction is sent over the network to the blockchain, where your public key is used to verify that it was you who created the transaction. You can tick a box in keychain to just post and vote without bothering you, but if you don't tick it it will ask you to give the ok to post/vote every time.

Example B: I go to hivedapp.whatever, I create an account, they ask if I want to give posting permission, I say no, I draft a post, I click "Post," it sends me to hivesigner, I give it my posting key, draft gets posted, I draft another, I click "Post," it again sends me to hivesigner, I again give my posting key, second draft gets posted. (Unless, I'm posting the second draft while hivesigner is still open, per the quote above, then I shouldn't need to enter it again.)

This isn't how hivesigner works. You use your active key to sign a transaction locally to give hivedapp the authority to only post and vote on your behalf. Once that authority is set, it's permanent, unless you revoke it (you can do that via Peakd.com I believe). So you only need to do that once.

So using hivesigner or keychain no one should be able to intercept your key and make malicious posts on your behalf.

Tagging @asgarth as he can give you the definitive lowdown on Peakd. Tagging @good-karma, as I think he's the wizard of hivesigner.