Guys, I have a terrible confession to make...
...it was me who told Polly how to fake GUIDs. I didn't do it maliciously, it was mostly out of curiousity, and I needed someone to test it. Now, of course, if what you're saying is true, it seems pretty stupid that I trusted them, and for that I'm sorry.
Personally I haven't used the knowledge since that night for testing, I've been using my qkey GUID (which Polly knows, btw). Also of note: I discovered how after someone with an anomalous GUID connected to Polly's server and he/she came to #tremulous to ask about it. It is therefore possible that neither I nor Polly were the first people to discover this method, and you might thank Polly for publicizing it and allowing it to be fixed.
To be fair, the bugzilla report on it does credit Polly for bringing the bug to the attention of the reporter, so if it were not for your accusations, I'd still be assuming good faith.
edit: I just got the IRC logs: #tremulous
and PM with polly (edit: removed for discussion of hax)
The #tremulous log contains everything I said to polly that night, so you might want to skip to the double line breaks I inserted if you don't care much about what we discussed initially (and tbh don't know why you would).
edit two: it seems there are some erroneous characters in those logs, something to do with character encoding I'd guess. I cba to fix it though, it's still readable. Suffice to say they weren't in the original.