They've done nothing wrong. People that pre-ordered are people who were going to buy the game either way, most likely, the Beta just gave them a better reaosn to do it now, rather than later.
The company clearly stated that everyone would have access at a later time, it could have been 24 hours, or two weeks from release date. Regardless of why they did what they did, the Greater Good of the Game supercedes all others! /Tau
Personally me, I wanted to try beta and see if i will buy the game. I asked via Twitter if they allow Alpha tester and they didn't say a word about it, so it looked like they no longer allowing Alpha testers, that's why i preordered.
They said performance increased 2.5x, but for me performance increase like 10% at best, which make game unplayable, and i am already regretting for preordering it. So don't say everyone would buy it anyways.