(Posted here for future reference)

XP whore, n.: a common PerlMonks idiom to refer to an individual who is more concerned with Experience Points (XP) than with what they're meant for, and would do anything for them, including undertaking unethical actions like plagiarism. Apparently first showing up in a node (as "XP-whores") shortly after the introduction of the voting system itself.

Also used is the verb "XP whoring", to refer to the act of behaving like an XP whore.