Over the last hour or so, reports have started flooding in that the PlayStation Network is gradually falling to bits. It started with people saying they couldn't access the PlayStation Store (and at the time of writing, that's the only issue that the official PlayStation website acknowledges), but now players are being booted from their online games.
The other main issue at the moment appears to be that users are unable to restore licenses for their digital titles. Before the process completes, many are being met with a maintenance error message, so they're essentially locked out of their own software until things get resolved. Hopefully that'll be sooner rather than later.
But yeah, if you're having problems, know that you're not alone and give us a status report in the comments section below.