Just lucky ? Or some tech glitch from facebook?

Today I got a chance to set the fb web address(people also call it "vanity url", "unique fb url" ) like "facebook.com/myniche" for the first fanpage during the creation process. It's really true cos I even tried to create the second fan page using another fb account on a remote VPS, I also got the chance to nominate an unique address for it.

The strange situation began after that. No matter which fb account I use to create new fan page, there were no more options for me to nominate an unique address for them. And when I tried to make it with an alteative way by entering the 'setting' window and manually set vanity name, I was told I will be qualified to do so after getting 25 likes for the fan page...

Why it showed me the different process reg. fanpage creation? Random procedure? Just lucky? Or tech glitch of facebook?

I'm new on fanpage...did I miss something?