don't think it’s bad, I get key logging junk all the time that’s sent right to my junk mail I’m sure. (Free blizzard mount giveaway, click here now for your free mount) They need to accept you and you need to accept them and if someone gets hacked they see your e-mail address, that’s fine, there’s a zillion (well just under) ways to get an e-mail address really.
I think the point of it is a way to communicate between close friends that play the game, not meant as a guild chat thing. In reality a lot of folks use ICQ/AIM/Messanger/Facebook/etc to communicate together while there in different games, all of those are hackable as well and they could get your info from that. The average person may have 3-5 people only, social butterflies may have many many more close friends
So I think its fine, just practice normal precautions and don't open any funky e-mails regardless if you play wow or not, use proper anti virus and if something looks to be to good it most likely is

And if you ever think blizzard wants to give you something never click on a link, log into the game and go to account management from there and you will see if its true
And if you practice safe internet’ing (don’t think that’s a word

) then you have taken all the precautions and you don't have to waste time being paranoid about it. And if something ever did happen after all that remember... it’s a game

Blizzard will restore everything. So be safe and have fun
(yes I rambled on )
