Basically every 1 account can be on 5 different PS3 systems. One PS3 using the account buys something, so the other 4 PS3 systems that has that account activated may as well download that same thing (with the exception of movies I think?). But only the 5 PS3 Systems that actually has the account may download/use the game. The only way to deactivate is by having one of the PS3s deactivate, which won't allow you to play the games anymore so you gotta stay activated.