If someone would come up with an unarguably better name, it would take, but so far have not. "Personal Vaporizer" says nothing about what kind of vapor or its purpose. If "personal" implies a purpose, it's probably not what it's actually for.
Language is built on the old. I note that even the big companies are trying to find a better term, e.g. markten's "e-vapor".
The best, to me, is "vapor cig". "Electronic" is kind of like saying "magic" more than explaining anything, so vapor's better. "Cig" implies some relationship to smoking, but insisting on abbreviating it also differentiates also, as well as using a stronger modifier in front. "E-cig" is still shorter, though.
If "cig" is such a bad descriptor, I guess everyone here still smokes because vaping doesn't relate to smoking or replace it.