From their website:
QUOTE
At NebuAd, we deliver behaviorally-targeted advertisements that provide incomparable results to advertisers, publishers, service providers, and most importantly, to consumers. NebuAd delivers these results through keen insight into a consumer's dynamic web-wide behavior, sophisticated and innovative methodologies and technologies, and the ability deliver the most relevant advertisement at the right time in the right place – anywhere across the internet.
See also this article:
http://www.techcrunch.com/2007/06/23/real-...ed-advertising/
Glad to see these bad guys are blocked!