I'm glad someones brought this up. I've often thought about this myself sometimes.
Here's a thought that occured to me a while back:
Program B accesses (i.e wears) Program A's Disk. He then runs off and has all manner of exciting adventures throught out the System before finally returning to Program A.
Program A then puts his own Disk back on.
The question that I've always wondered is, what would happen?
* If only Program A's memories can be stored (or 'synconised') onto his Disk, would that mean that everything Program B did/saw/remembered would not be recorded on there?
If that's the case then that would cause all manner of problems-Program B could run around commiting all manner of serious crimes (theft, terrorism, maybe even MURDER) and yet by wearing someone else's Disk (which doesn't record his actions) would avoid being prosecuted because of it (assuming he gets caught-his own Disk wouldn't be used at the time, so therefore wouldn't hold knowledge of his actions thus meaning he wouldn't be charged due to a lack of evidence).
* Would everything that Program B did be stored on there too along with Program A's memories (thus creating two sets of memories-like creating two Folders with differant information on them in the same department).
If that was the case, then other Programs (Program C, Program D, Program E....) could do exactly the same thing with the SAME Disk, which means that that Disk would get pretty full up quite quickly.
With all that additional information/data crammed onto it, this could cause some damage to the Disk, which (I would imagine) would really upset the original owner. :-s