Update: The PlayStation Blog has added an update to its US portal this evening that suggests the service disruption may continue for a good while longer -- according to Sony's Patrick Seybold, the company is "rebuilding our system to further strengthen our network infrastructure," and working non-stop to do so.
[Thanks, Christian and Joe]
An external intrusion on our system has affected our PlayStation Network and Qriocity services. In order to conduct a thorough investigation and to verify the smooth and secure operation of our network services going forward, we turned off PlayStation Network & Qriocity services on the evening of Wednesday, April 20th. Providing quality entertainment services to our customers and partners is our utmost priority. We are doing all we can to resolve this situation quickly, and we once again thank you for your patience. We will continue to update you promptly as we have additional information to share