Baron should be able to prove he deposited money into his lr account at least.
He could even take screenshots...
Liberty Reserve has an SSL certificate by VeriSign Inc. ("Class 3 Extended Validation" it says, issued in February, for 2 years). I think VeriSign certificates cost quite a bit, and VeriSign is pretty reputable (used by banks). In the VeriSign website, they say they give "warranties" of more then $100,000 . I.e., if you can present a false certificate issued by VeriSign then, congratulations, you win $100,000.
These "certificate authorities" simply vouch that "you are talking to the real Liberty Reserve" or "you are talking to the real mtgox.com" (or to whoever has mtgox's server's private key). It's still up to you to decide who to trust. My idea was that maybe this could be used to prove ["prove" or at least "show", with a relative degree of certainty... measured in dollars perhaps?] that this particular communication was really between mtgox.com and baron, for instance. In the absence of anything else (like a PGP-signed email), this could work as an on-line "statement" or a "receipt".
If the website says "your balance is this", in a way that any human could understand, then that's an obvious statement, isn't it?
I still haven't looked into the technical details of this. It will probably require special software in the client. Passwords would be included in this conversation, so, after recording, the client would have to change the password (and record the password-changing conversation too? he wouldn't show that last one, of course). If the website in question, at some corner, shows the current date/time, that is good (a statement that "this is the time now").
It's probably too late for all that now. Baron should had thought of this earlier. MtGox and friends can say whatever they want now.
And where are those $3000 LR transactions from Baron to the alleged thief?