Don't really have my own view on this particularly, I've not read up enough. I listened to a pretty lengthy phone-in last night and the basic view is that genuine recipients of incapacity benefit don't want to be tarred with the same brush as the feckless members of society, and they find it is absolutely central to being able to live their lives.
Of course the flipside is that nobody wants the lazy bastards to be able to cheat the system. How do you crack down on one but not the other? Re-application of all has been suggested - again, this was met with contempt by those who actually belong on incapacity benefit.