As I understand you are officially allowed to share downloads from the PSN Store on up to 5 other active PS3s. Free games you can ofcause download on any unit and downloaded items I think work the same as 'pay for' Games. With the exceptions of expensive games like Warkhawk and GT5 Prologue you can do this with every game as far as I know.
To share them with another console you need to sign in on that unit with the Playstation account that purchased them initially and download them accordingly. If all the 'owners' of a game (the original purchasers) are deleted then the game will not work, so you must keep that account on the PS3.
The only problem I can think with this is if you buy a game say Flow for example and want to share it with a friend; so you sign-in on their console and download Flow. All things are fine.
Say some time after, you download Super-Rub-A-Dub but don't want to share it with the same person who you shared Flow with.
Either (a) they download it anyway by logging in on your account that is still on their system. Or (b) you ask them to delete the account in which case they won't be able able to play Flow so atleast one of you is going to lose out.
Can anyone who has had past experience with sharing of content confirm or refute the above, and any other potential problems with this system?