this seems like they want you to make a purchase decision after one play through of a demo. i don't know about anyone else, but i usually play a demo through many times to make the decision if i will buy the full game or not. and demos like the psn title tank battles, are far to short with the time limit. i was not able to make an informed decision to buy the game after playing the too short demo, so for now it will have to stay un-purchased by me. and seriously, with how short demos are as it is now, and how limited they are, there should not be any more restrictions placed on the demos.
this idea is obviously driven more by greed than any other factor. it's not like developers are losing any money by consumers playing demos for an infinite amount of time, as they are payed in installments by a publisher as the game is being developed. publishers are also not losing any money by consumers playing demos indefinitely. they are not making any more money from demos as they are now, but they are not losing any money. it's not like people are hacking/cracking demos to get the full version of games without paying for them.
hopefully it will be up to the developers whether they put self destructive qualities in their demos or not. if it becomes mandated by sony, i for one will not be downloading any more demos. i know that one person doing a solo boycott will not change anything, however i stand up to my principles no matter how unpopular or how few other people agree with me.