Vicki-
That power is supposed to be used only to enforce an already-existing ban: it was created to deal with Michael's endless aliases and can reasonably be used in any similar situation. It doesn't mean that any sysop--of whom, as you note, there are many--can exclude someone from Wikipedia. That way lies instability at best.
It was always allowed for developers to ban signed in users in cases of obvious vandalism. Now that sysops have the same ability, I see no reason why it should remain limited to people such as myself.
Regards,
Erik