Sadly the majority of our flight deck visitors are morons who are bored. The rest are usually charming people who show a great deal of interest and attempt to ask the questions they've 'always wanted an answer to'.
The Cabin Crew do work their *rses off on the short sectors as stated above and cannot always 'vet' visitors - a business card works wonders here.
Personally, I feel that we are not 'part of the IFE' and would keep the door closed to all but those (as above) with a professional interest.