The fact that pundits, ex refs, loads of other dikheads, and more importantly us (the real experts) can't decide conclusively whether it is offside or not basically makes a mockery of the rule.
It was offside by current definition as I know it it, but irrespective it is time for a change of the rule as
@mudshark says.
In short you are trying to affect play or you are not. IMO if you are walking/jogging/running/limbo dancing away from the action then you get a pass. Otherwise you are affecting play and are offside.
I also think on the defensive side, if you are injured/prone on the pitch then you are not counted as a defender for the purposes of offside. This is open to abuse I guess but the logic makes sense to me.
The rule has got too convoluted now and needs simplification.