Ok, I've seen a bunch of speculation of why people think PSN is down, and I thought I should just post what the community knows in comparison to what Sony is telling everyone. The truth is, there was a new CFW (custom firmware) released known as Rebug (You must login or register to view this content.). It essentially turns a retail console into a dev console (not fully, but gives you a lot of the same options that usually dev's only have access to). Anyway, this new CFW was quickly figured out by 3rd parties (not Rebug) to give CFW users access to the PSN network again via the dev networks. With a little manipulation of the URL's through a proxy server you could get your hacked console back online. Not that big of a deal, right?Well, it also turns out that some people over at NGU found out that you could provide fake CC# info and the authenticity of the information was never checked as you were on Sony's private developer PSN network (essentially a network that Sony trusted).What happened next was extreme piracy of PSN content. Sony realizing the issue here shut down the network. Now, before you go freaking out about the latest information posted about Kotaku, no ones personal information was accessible via this hack. Not to say they couldn't get it, but no one is admitting to it being available. Anyway, that's the real reason for the PSN downtime. Sony is now rebuilding all of it's PSN servers to be more secure and (hopefully) make sure the CFW users cannot get online anymore.

Edit #1: To those of you saying that this is speculation, you are correct. But, it is speculation based on a lot of facts and the outcome seems to make the most sense.
1. Rebug was released on 3/31/11.
2. First guides of how to use the dev network to get back on COD games on 4/3/11. 3. Word of "shady" sites finding a way to pirate PSN content via the dev networks on 4/7/11 (basing this on posts I had to delete on the website). 4. PSN goes down on 4/20/11

So hackers find out how to duplicate PSN ID and get free games, Sony then gets PWNED by more hackers thus shutting us from PSN For over a week and those hackers could use CC info yet YOU ONLY find blame in Sony?

Hacking is fine but not when it ****s us over. If Kanye West sues me for ILLEGALLY downloading his music I wouldn't try to protest because I know its illegal.

When 360 puts their banhammer for pirated 360 games I don't feel sorry for console bans. Sony is pissing me off but the nerds that did this shit are worse.

Sony has internet, all they have to do is look online to see who is pirating and how.Most hacks nowadays get fixed because Youtube whores post video tutorials which help companies fix things as much as helping hackers.

I totally agree.. there needs to be some kind of underground (Illuminati) type of structure in effect when it comes to this. All these n00bs are the reason why Sony is succeeding. **** Sony this is a free world.. what ever happened to Democracy? Sony = Adolf Hitler lol