Because people may want to post on tech support forums
or reply to community events being arranged on the forums.
Neither of which you will be able to do without revealing your full name.
Rumor is that blizz employees will be exempt from the real name thing "for security reason"
edit - seems the panic is over. Rumor update "Real Names on official forums cancelled."
the 50k+ angry posts on the offical forums must have made them see sense.
(
Lanc Weekend Trailer Park Supervisor, Fri 9 Jul 2010, 17:30,
Reply)