WoW forums depress me

[apandapion]

This makes me wonder why on earth they then say 'only people from NA can participate', when clearly some people from Europe are in the beta.

Just to keep things simple. "If you're not from north america and you haven't been invited, you're not getting in" would be more accurate, but simplifying it to "Only those from NA need apply" is perfectly reasonable. If you make it look like there's any slack in the nationality of those who get in, you just get more begging emails.

And it also makes me wonder why they put that limitation up. Why not just open it for all countries and then sort the people they want?

Can you really not think of a reason? I can think of several. They're probably paying attention to the ping times, and having people from across the world, especially when most of these people will be playing on a closer (local) server when the game launches. You want to beta the server under the condtions that it will be playing under, and those conditions are : most people play on the closest (or a rather close) server to them.

Having people from other countries can (does not always) raise communication barriers.

NDAs may be more complicated on a multi-country basis. Having a couple trusted non-americans might be ok here, but having lots of people from lots of different countries might be a legal fiasco. On a similar legal issue, they may have concerns about shipping the beta to countries where reverse-engineering laws and hacking laws are different. Wise hackers hack outside their own country to complicate legal issues - shipping the beta to remote locations with laxidasical law enforcement is simply not wise. Better safe than sorry would be my watchword - you'll find plenty of beta testers in the US. Instead of hiring a fleet of lawyers to explore the legal issues, why not just keep it close to home?

And why does Korean need it's own beta? Is that only a sales-trick?

Korea is both a very different market and a very large market. Testing specifically in korea is a good move.