Last Thursday, about a week ago, Belfaire acknowledged there was a problem on the forums, and asked people to enter their names if they'd input their beta keys and hadn't recieved a beta email (here's the BlizzCon thread, and here's the Dell thread). But there's been no answer since then, and I certainly haven't recieved a key at all. In fact, we've heard from people who got invited to the beta through the random opt-ins, which means these keys we paid for haven't done thing number one for us.
To tell the truth, I'm not that concerned about it -- I really enjoy seeing new content on the live realms rather than on the beta or test server, and there's certainly enough Wrath beta news coming through here on WoW Insider about the beta to keep me satisfied. But the beta is only going on for so long, and every day that passes without invites sent to Blizzard's biggest fans (the ones who've spent money on the Dell deal and attended Blizzard's invites) is more of the beta key wasted. I doubt we'll be able to use them again, so it's a shame Blizzard hasn't let us use them yet.
Thanks to everyone who sent this in!