It woud be nice to add a animation to each vertex or vertex group. Just
loc rot and propotional set. Not always you can use armature to make a vertex animation...
I don't know what you're after but you can in fact animate vertices. Just select vertex and press I -> mesh. Move it, add time, do it again. You can select many vertices at once, works with proportional editing.
That is vertex keys. They are great! You can do relative VKs by clicking the "relative keys" button in the anim buttons (little squiggly line under main 3d window). That will allow more complex, IPO driven animation, perfect for reusing moves, like facial movements on a character.