Always dog-ear. Sure, it's a bit paranoid, but I'm always afraid the bookmark will fall out somehow =_= it has before, so I cannot trust it... Plus, if the dog-ear unfolds, you can still find your place because of the crease :) HOORAY FOR DOG-EARS!! :D
I dogear them. I also sit drinks on them... and pile things on them in my packpack that bends their covers... and leave them in the floor for puppies to maul and/or widdle on.
It's tough love. XD