I'm surprised by their extensive list of customers, and also the fact that customers seem to be happy to be identified as their customers ... http://www.demandbase.com/who-uses-demandbase/customer-list/

Hardware manufacturers & telecomms seem to feature heavily:

(a selection) ... Adobe, Dell, IBM, AMD, Box.net, Cisco, CSC, Comcast, Freescale, HP, Lenovo, Motorola, Novell, Qwest, Salesforce.com, Siemens, Symantec, Verisign, VMWare, Vodafone.

And there's several anti-virus/anti-malware companies listed there.

UPDATE: The LeadLander.com site also lists their customers - Microsoft, Motorola, Red Hat and Cisco, among others.

I wonder why some of these sites would want to participate in an information exchange that seems rather asymmetric. I couldn't find detailed information on the service but I assume they have some kind of mechanism, similar to those in P2P systems, to "encourage" sites to contribute large amounts of information(?) or maybe sites can buy information without having to sell?

Just checked, looks like Ghostery blocks Demandbase.

AdBlock is for blocking (annoying) ads, not trackers.

Depends on the filter list. EasyPrivacy is designed to block trackers, and if you look at the list

https://easylist-downloads.adblockplus.org/easyprivacy.txt

you'll see that Demandbase is there.

Well it does seem to block some retargeting pixels -- and this seems like a worse form of retargeting.

AdBlock blocks requests by URL matching and hides DOM nodes based on a handful of selectors. Whether this blocking and hiding is targeted towards ads or not is incidental.

Ghostery does, though.