Lanefan
Victoria Rules
I'm not exactly an easy-on-the-characters DM but even given that I've always thought Ear Seekers were a dumb idea. If I've ever DMed any it was so long ago that I've forgotten doing so, and it's very highly doubtful I'll ever DM any in the future (though I've learned to never say neverSee, this comes across to me as a pretty degenerate methodology. You want to encourage people to listen at doors, that is a major part of play to prevent players from being ambushed by monsters behind doors. And the solution to ear seekers was... getting a listening horn, to listen at the doors with. And then you "got complacent" doing the very thing that the game wants to encourage you to do!

That said, in moderation I love throwing in the occasional Trapper, Cloaker, or Lurker Above as, in effect, a living trap.