Demo's are getting larger and larger recently, often an A1 title the demo comes in at way over a gig in size, this is bad enough when teh demo only gives u 1 small level or 30 mins of game play, but can u imagine a demo of a game full size such as AVP (15 gig)of BFBC2 (20 gigs) no way will i bother downloading that for something that will only last a couple of hours.
I am not concerned about pirates, we have always had them, for way back with the commodore 64 and the Sinclair spectrum, there always will be pirates (for the foreseeable future anyway)and this system wont change it at all, as long as the pirates can be kept away from the MP side of things balance is maintained.
It is in fact a good idea, but premium products are far to large to make it practical in my opinion