My thought was that one of the main points of having inline adjusters is that you could make adjustments on the fly, without having to stop riding and make them, start riding to check, stop riding to re-adjust, etc. It's nice to have adjusters at hand while riding in order to fine tune adjustments.
And considering this, I would put them somewhere between where the cable comes out from under the tape on a road bike, and the first frame cable stop.