It looks like it is an issue with the registration services. I was actually looking at re-activating my account, and saw it was now down for maintenance.
It's been down for "maintenance" for some time now and I'm pretty sure it's not maintenance, that's just how they are making it inaccessible. Plus that's not really a huge problem since many people have already registered for beta and just need to enter, they could fix it while the game is being tested by those who are already in the beta.
In other words, I doubt it's that.
I don't think there are many things that could actually delay the beta because...well, it's a beta, it's supposed to be buggy. The only thing I can think of is some serious problem like a memory leak somewhere that opens the system to security issues.