Sony had a rough weekend. In addition to their PlayStation Network was taken down with a Denial of Service attack and then were further crippled when their Sony Online Entertainment service was also taken down. Microsoft didn't escape unscathed either as their Xbox Live login servers were also knocked offline in a world wide hack on these gaming services. Reports are floating around that Battle.net was also affected and this caused League of Legends to be unavailable for a while as well. Thankfully for all of these services, no information was taken and nothing was compromised - logins were just crippled due to the DoS flood.
As SOE's John Smedley explains, the culprits are simply trying to overwhelm Sony rather than break in. That won't be much comfort if you wanted to squeeze in a few rounds of Killzone before the weekend was over, but it hopefully means that you can get back to playing without worrying that your data is vulnerable. In at least SOE's case, some services are already back up and running -- give it a try and let others know how it's going in the comments.