I am personally for "no lives", because otherwise you get killed early on by a freak mishap and then you gotta sit and wait ten minutes for everyone else to give up and die.
I agree.
Having lives will make the atmosphere a "last-man-standing" genre, and because nobody really wants to wait for the last guy to finish, it should be limitless. Though having lives on might increase the effort in teamwork, it's disadvantages outweigh the benefits in the long run, like the example above.
Besides, who really wants to play SCP on the "Keter" mode anyway?
Possible coward position?
That'd be funny.