But now - obviously - you guys are randomly generating Letters of Guarantee which are signed with another btc address. Here is my letter of guarantee which I received from your website, see for yourself:
~letter~
You should have checked the letter
before sending the coins, then. Its purpose is for you to verify you can actually accuse them if anything goes wrong.
I doubt they would randomly generate invalid letters to random customers when someone could be verifying every single one of them (as they should).