I agree typing "uk" isn't difficult, but when threads are started in the classifieds and the poster forgets to put it in, you get the half a dozen posts pointing out the error before the mods get chance to remove it. Then the guy opens a new thread asking why the original thread has been removed, and you get the same half a dozen posts telling him he should have put "uk" in the title.
I've just looked back through the last 6 pages in the for sale section and only one has not got "uk", it's got "eng".
Surely this rule is getting a bit redundant, and causing more hassle than it's worth.