Here you can see how many PS3's are activated under your PSN ID – http://www.qriocity.com

Important change in PSN activation policy:
From November 17, 2011, you will be able to activate only 2 systems, instead of 5. Content purchased prior to that date should still work on up to 5 PS3's, though I am not sure how that activation process works on the 3rd, 4th and 5th PS3's. Please let us know if you have experience in getting old content to work on more than 2 PS3's on yet un-activated PS3's. Older content on earlier activated 3rd Ps3 worked in my case even after that time, but that PS3 went the YLOD way, and I couldn't test if older content would still work on a yet un-activated PS3.

Here's the old post, just replace the 5's with 2's.:
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PSN allows you to download your beloved psn games up to 5 activated systems at any given time. What this means that you can have the games installed on infinite number of PS3's, as long as only 5 are active at a time. After the 5th ps3 with you account active, to install your games on a 6th PS3, you must deactivate an account on one of the 5 systems. Here's how:

Boot up your XMB, sign in to PSN and then follow:

Playstation Network -> Account management -> System Activation -> Ps3 System -> Game / Video -> Deactivate

Here are some very important points:

• Deactivation does NOT erase your account on the system.
• Erasing the account does NOT deactivate your account!

Therefore, it is of utmost importance that you deactivate an activated account on a PS3 before deleting the account on that PS3. If you forget that, you should add your user to the PS3 again to be able to deactivate it. When is this important? If you send your PS3 to be fixed but they send you a refurbished unit, you might have lost one of your 5 activated accounts. How to solve this problem is beyond me, but you can share your experience if this happened to you.

Here are two more things that I am not sure about, please correct me:

• Activation of an account is automatic when you first download a game from the store using that account.
• Activation does not occur simply by logging to PSN using a PS3.

The Game and Video is ingeniously seperate, while they probably have different DRM restrictions,[update: JimmyStewart reports that video's are activated only on one PS3] it also helps to know that you can share videos without having to worry about your games and vice versa. Here is my extra 5 cents:

• Do not share your account information with strangers. The 5 ps3's you can download to are PS3's you own or you play on.
• Make sure you share your account with people who you can ask to deactivate when need be.

 Please correct me if you find any of the previous information to be incorrect.

This can also be done with the PSP. Up to 5 activations to one account. Also not all games support up to 5 systems. I think games like SOCOM and Warhawk are one activation per. I\'m just saying.

Emrah said:

The Game and Video is ingeniously seperate, while they probably have different DRM restrictions, it also helps to know that you can share videos without having to worry about your games and vice versa.

Man I wish I read this thread a few months back after getting my slim.  Grrr….

Anyhow, this can be updated.  For videos you're allowed only 1 PS3 activated at a time.  For me this means I have to track down my old console since I was entirely unaware this sort of thing was in place.  I've got three videos they gladly charged me for that I can't play on my current PS3s.  Even if some sort of legal work keeps them from allowing the same plentiful 5 PS3s that the games enjoy, you'd think they could at least cover three consoles.