Er, I've heard about whitehat, blackhat and greyhat hackers, but not about panthers? LOL.
If this is true, it's clearly just a spin-off of that.

The system went something like this:
White hat hackers: All about ethics, hacks strictly for uh.. just purposes? Not ENTIRELY sure how that works..
Grey hats: Stuck between white and black, they have some regard for ethics, they're not just going to hack anybody, but if you pissed one off badly enough or if you had something they wanted they might.
Black hats: They don't care about ethics. Basically they'll hack just to see you cry.

Should ask Sothe about it I guess, he's more familiar with this stuff.
Dunno where you heard that they were being called panthers, but it sounds to me like whoever was calling them panthers was maybe just poking fun at 'em.
Sounds more fitting to me anyway.

But this isn't just PSN related, I think this is hacking in general.

Sloppy post is sloppy.