David. You and the other moderators have done a fantastic job of catching this kind of thing at source. I have seen very little get through since I have been here and when it has, a number of APUGers with "keen noses" for this have acted swiftly.
Funny this should come up now. A group of us were discussing "unwelcome intruders" at lunch during the APUG tour of Ilford on Friday last. Given our numbers and the size of the site we are well marshalled and I am sure we'll all keep our eyes open now.