I think I called someone in my previous guild a $*@%ing tool or something to that effect. That probably burnt that bridge.

Check them out every bit as thoroughly as the guy in T4. "Burned some bridges" is sometimes not the half of it.

I'm on a lower-population server, where there's only been 2-3 serious guilds going beyond Mags and Gruul at any one time, for most of BC. Mine is one of those. Once, while we were at the end of Hyjal/mid-BT, we got an application from a transfer fairly decked out in full T6, Illidan staff and trinket, etc.

A little asking around on his previous server found he was a disliked and disruptive guild-hopper. Realm forum shenanigans after he was turned down further revealed that he was also a serial guild bank ninja who'd been transferring, ingratiating himself with high-end guilds, and stealing as much as he could to leave again on every transfer cooldown.

The bottom line, is to ask for references. If they can't give you a little "employment history," so to speak, that's a huge red flag, no matter how well-geared they are.