whitelist ends up as a greylist
there was a discussion regarding WL's on spam-l and a few people admitted using commercial WL's as a "greylist". Basically it is assumed that people only (pay to) join a WL to get thier commercial message out. So instead of letting such trash through you let S::A add a NEGATIVE score if thier ip is on a commercial whitelist.
Given the recent messagelabs originated volume UBE and my spamtrap reporting fiasco
where ML was asked by the client if I would gve them the domains of my spamtraps :-)
IMHO addition of ML or any other "commercial/TBTB" will prove to me that the WL is tainted.