edit: If the information that was compromised allows an unauthorized individual to log into our character accounts, the damage they *could* sell most of everything you own, trade your tradeables (I'm sure they'll have fun with four items at a time, hahaha ~ ahem, /equip Serious Face :-| )
And this isn't SE specific, so results may vary, but a step further is to lock you out of your own account, change the security questions, and alter the password recovery e-mail. Gives them more time to conduct their unsexy and unauthorized touching of our avatars *compromises a certain translator's subligar security*
A step further is to compromise the e-mail account associated with the main account. And there's a good chance people use the same password for multiple accounts, so it's not too much time to crack it.
Loss of time invested. Frustration of trying to get recovery. Mid-worse case, you're not believed by the company that you were a victim of theft and do not get reparations.