I just put another user on my "ignore" list for the first time, and found that I couldn't seem to put him on that list and the "contact prohibited" list at the same time. Personally, when encountering a troll, I'd like to be able to do both, so for me it would be as if the guy didn't even exist. Kind of like entering somebody both into one's mailfilter and killfile, back in the days of Usenet. I'm guessing that other people might like to have this option as well.
Would it be a difficult thing to program into the system?