I would have thought that Beth wouldn't give the codes to the new people that just joined... I mean, maybe a couple to have a varied group of testers, but why not take post count or join date into account first?
I play on the Ps3 so I hope all your Xbox's implode at the loading screen, but at least it would be to people who deserve it..
Are post date or join date even relevant? I'd say no.
If someone joined 5 years ago and has a post count of 10,000 and has never been warned, I don't really see that have having any relevance to whether they should be selected for the Beta as compared to someone who just joined and has a post count of 17. It technically only takes one post to report bugs if you're keeping a comphrehensive list and do a dump all at once, so you don't really need them to be glued to the forums as much as you do to the game. Then, when they've played or if they run into something in deperate need of fixing, THEN they come back to the forum to discuss it. You need to see a wide variety of iterations. Post count and join date could be mutually exclusive from beta testing ability.
How many characters have they played? Which races? What play styles? What's the average play time? What quests do they typically complete? Any order to that questing? What level are their characters?
The answers to those questions are far more relevant when taken in combination that when someone joined a forum or how often they post.
JMO