yes it has been done, but i will be nice enough to give you the link:
http://spacemods.googlepages.com/Traps3.zipits the Trap Bricks V3, it comes with lots of other traps too that you can make stuff with
EDIT:
There are two server prefs you can set using the console:
$Pref::Server::TrapSpawns = "X"
This sets the max number of traps in the server to X.
$Pref::Server::TrapAdmin = "X"
This sets whether only admins can place traps - X=0 for anyone, X=1 for admins.