Is it a surprise?
Think of all the services n PSN
Account management / New account setup
Credit card / points management
3rd party single sign on (e.g. Netflix, iPlayer, Hulu, games etc.)
Other 3rd party services, e.g. Facebook integration
Messaging / Voice / Video chat
Firmware updates service
Qriocity front end
PSN+ subscription service
PSN Store native PS3
PSN Store native PSP
PSN Store PC / Media Go
PSN Download servers (possibly geolocated for performance)
Game servers for all Sony games
x3 all of the above for each region.
They had to go physically relocate all the hardware, bring all the network back up, security harden it, and go live again. While you can slag off Sony for the breach (though details are still not forthcoming), it is no surprise it has taken so long to bring itself up once the extent of the issue was disclosed. From Sony's perspective I guess they don't want to bring it up and see it all collapse again so they phased it with the non-commercial stuff first and later PSN. The interesting part will be to see how the service copes when everyone goes to grab their free games.