I don't think that what you are trying to achieve can be reasonably done using regular expressions. If you say they pro/retroactively make up new domains to prevent you from blocking their sites, you'd end up permanently changing and testing your RegExps. Domains are cheap, if I was the NSAADS guy i'd simply buy NSSAADS and NSADS and whatever comes to my mind as well.
I don't think that what you are trying to achieve can be reasonably done using regular expressions. If you say they pro/retroactively make up new domains to prevent you from blocking their sites, you'd end up permanently changing and testing your RegExps. Domains are cheap, if I was the NSAADS guy i'd simply buy NSSAADS and NSADS and whatever comes to my mind as well.