I've been looking at it a little more carefully, Blockchain is starting to bill themselves as an exchange, and the KYC is for trading in that capacity.  I think they are using this air-drop to lure people to use their new service, but to get the air-drop you need to submit KYC.  I don't think the staff of Blockchain will do anything nefarious with my info, and it's not like they can glean much information about me from my driver's license.  None the less, I think I'll pass for now.