dr: good morning. i think there are not "artifficial mattes" often used. if i catch your meaning well. did you talk about film borders like this http://www.fstop.cz/e/slavik/day-dreamers/ for example? yes, they are used some times, but i'm not sure if often. as i said before, i love big white borders, even on wall. maybe ive got probblem within. :) i really must read some kind of book about it.
have a nice day Douglas.