Lock bumping is trivially easy as long as they have the blanks, which you can buy on ebay. It is not like picking a lock, in that it requires basically no skill, and takes only as much time as it takes to unlock a door normally.
It would be a right hassle if someone did you this way, as unless they left obvious marks, and you got forensics in to look at them, it would look to the insurance company like you left the door unlocked.
But I don’t think it is at all common currently, or else we’d be hearing about it in the press, in things that aren’t releases from anti lock bumping companies, and insurance companies would be stipulating changing of locks. You do have to carry a bunch of dodgy bump keys, one for each type of lock (like blank keys but with special ridges cut on them), which is a bit of a hassle (and counts as going equipped if you get caught).
I thought that greasing locks made them easier to bump, but maybe not if it is very thick grease they are selling.
Joe