It has always seemed a little excessive that you can download one game and play it on five machines. I mean, I get having a PSP and a PS3, and maybe a spare machine - but five? Anyway, Sony's putting an end to that from the middle of November, reducing the activations from 5 to 2 FOR NEW GAMES ONLY.
That means you can still have your old PSOne games or others across your PSP, PS3 and Vita - and will only need to download new games to your Vita and PS3. Makes sense to me, I'm sure a lot of gamers will moan, as they always do. If you have games registered to a bricked PS3 or PSP, you can use the website to deactivate them for installing on newer machines.
UPDATED - Sony's blog has the formal news
Sony says this is to keep the copyright holders happy, and if the Vita and future PS3 games *cough* Grand Theft Auto V *cough* are going to be downloaded by the majority only, then its fair enough. The update will take place in mid-November in Japan and presumably by rolled out everywhere else shortly after.