There is definitely 0 reason that they should be scanning all of the files on your computer and storing them in some sketchy gibberish registry settings. Who knows what else they are looking at.
This is no different then Sony putting rootkits on their audio CD's in order to "prevent piracy". http://en.wikipedia.org/wiki/Sony_BMG_copy_protection_rootki...
Can you expand a little bit if you have some knowledge on the subject?
Edit: I did find mention of it on the Wikipedia article about Warden: http://en.wikipedia.org/wiki/Warden_(software)
On 23 June 2010 Blizzard updated the Warden Anti-Cheat Platform to version 2 - named Warden 2.0 - with World of Warcraft Patch 3.3.5.
Warden now scans Warcraft II and III game memory space only, with exception of a few tools.
Obviously it's a Wikipedia article, and no source listed for that claim, so who knows if it's accurate.