Aren't these really just the kinds of terms that savvy marketing departments concoct to make their products seem better than they really are? "You have WAN optimization, but do you have WAN acceleration?" "Their product will only accelerate the app. Ours will optimize it."
This would all seem rather silly were it not for the very real possibility that network administrators will start to fret that they don't have the right mix of WAN/app optimization/acceleration doodads sprinkled about and will start to blow capital budgets on a bunch of stuff they don't need.
It's a good thing none of us has ever fallen for that, right?