Today's maintenance on the PlayStation Network will make it possible to activate three portable gaming devices on the Sony Entertainment Network.
From 9 a.m. to 2 p.m. Pacific time today, the PlayStation Network will undergo maintenance. Several minor improvements will be implemented during the maintenance, but the main accomplishment will be increasing the number of activated portable gaming devices on all Sony Entertainment Network accounts to three.
The maintenance will not disrupt online play or access of apps during the five-hour window, but a maintenance notification may appear when attempting to access the PlayStation Store, PlayStation Home, and Account Management. These three services will be unavailable. PlayStation recommends anyone wishing to access the network during maintenance to sign in to PSN now. If you haven't signed in within a few days before the scheduled maintenance, you won't be able to play online or use apps. Maintenance begins at 12 p.m. for those in the Eastern timezone.
While Sony only has two portable gaming devices, the PSP and PS Vita, this does help anyone sharing an SEN account who also doesn't share a gaming device. I can see this potentially being useful to families. There's no need to set up a new SEN account for children when you can activate their handheld on your SEN. This will also be helpful for anyone who happens to have three Sony handhelds lying around hoping to access PSN content on all three. The current number of portable gaming devices you can register on a SEN account is two.
Source: PlayStation Community Forums