WIll you be able to Soultrap in Oblivion? I f so, what types of sould can be trapped. My favorite was trapping Golden Saints to make a variety of Constant Effect enchantments. Can NPC's be trapped?
Since you need soul gems to recharge all magic items now (they don't self-recharge over time), I would have to assume that you can soul trap. However, like certain other things, it may be possible that it is a perk for Mages Guild members only. You may have to work up to being able to do it as opposed to just buying the spell at level one. Just speculation, of course