The incentives go away if the contract isn't extended... They also free up the CID namespace so they could be consolidated by a community or an archive... of course any other system can keep them as well... but yes, the problems now are the same as the problems in the future. If Geocities or Google Video go away, the content goes away. At least in our future if we go belly up, there won't be any legal way to stop a backup copy from being made.