Today PlayStationLifeStyle.net (linked above) reports that Sony has implemented a PSN notification system for sending messages and advertisements to users, such as when game demos have been upgraded, using their own ID simply titled [PSN]
Apparently this PSN notification system has already been in place on the Hong Kong PlayStation Network, but is new to other regions allowing Sony to communicate directly with members without relying solely on PlayStation Blog updates.
To quote: "Not only did I find this message, but an attachment. Normally, it is only possible to attach images in messages on the PSN, but this message contained an attachment that actually took me straight to the Earthworm Jim HD section in the PlayStation Store, pretty cool eh?
Additionally, users are also reporting that similar messages have been tied to titles in the 'Sam and Max' series, which leads us to believe that, yep, PSN in-box advertisements, which some may consider spam, have arrived."
More PlayStation 3 News