Frankly, I wouldn't use TOR for anything really secure
I rarely use TOR/Onion routers, and then I only use them out of frustration to overcome the irritating IP location-based blocking (watching online TV outside the viewing region and such).
It seems to me that trusting TOR with anything truly secure is a dangerous move. I do not believe--nor I'm not convinced--that the internet can ever be truly secure when messages are sent, say, between Alice and Bob and both their IP addresses are known and linked to them personally.
The internet cannot work unless IP addresses are 'published'. And as we've seen with recent revelations, government has back-door access to all those IP addresses--and probably access to servers along the way which would allow man-in-the-middle attacks.
With government having so much access to the internet, and with its very powerful pattern matching capabilities aided by super computers which are triggered at the first sight of encrypted text, you'd be mad to trust your secrets to the net.
Moreover, no one has shown that programs such as Mozilla Firefox can ever be truly secure.
In my opinion, TOR/Onion routers etc. should only be used in once-off emergencies such as a dissident trying to escape an oppressive regime.
A few high profile cases such as this might eventually serve to warn the world that the internet can never be truly secure in the same way as most us know that you never say anything on a public telephone network that you don't want the world to know about.