I'm not going to vote in the poll because I have my own ideas of what "soul-trapping" really is. I don't really accept the game's definition of soul trapping, with one exception.
Soul trapping and Soul Gems are, to me, actually a misnomer. What you are actually doing is harnessing the magical energies of a dying foe. Upon death, Magicka leaves the individual's body to return to the Void. "Soul-trapping" instead redirects this flow of Magicka into a material vessel: the Soul Gem. The stronger and/or more intelligent the creature, the more Magicka they exhume upon death, thus the Gems must be fashioned to be able to contain certain amounts of energy. This energy can then be bound to other material objects to grant them magical enhancements, AKA: enchantments. But this process does not touch the soul of the being; it simply interacts with the Magicka exiting their body.
Black Soul Gems, on the other hand, really do rob your opponent of their soul, along with the Magicka they harness. To create them is to practice Necromancy, as they are needed to fuel Reanimation and they steal souls away from the Afterlife which are needed for just that.
All things considered, I feel that makes good enough sense to me.