At the inFamous 2 Comic-Con panel the game's developer's from Sucker Punch hinted that the game would indeed have multi-player, as well as Move and 3D support. 

With a sly smile the development team on the panel had this to say when asked about the possibility of multi-player. 

"A lot of people on the floor have been asking us the same questions, which is, multi-player, about the Move technology and 3D support. We don't have any announcment on that today, but again stay tuned." 

For fans of the first game the idea of Move and 3D support together is a match made in heaven. Just imagine gliding from roof top to roof top in 3D and while taking out foes with your Move controllers in hand.

Source

Think they are gonna do a UC2 with this one by giving us a brilliant experience on all fronts of the game....the multiplayer should be crazy fun with all the moves and the weapon attacks might be fun with Move implimented...GC can't come soon enough I tell ya aaaaaaargh

Multiplayer sounds nice, hopefully it will turn out well. Right now I can't fully imagine how mp in inFamous 2 would look like.

Can't wait for this game. 

GOTY 2011. You heard it from me first. 

Does anyone else see the potential in a Move Controlled Infamous?   It would be Sorcery on steroids to say the least. 

Yeah especially with his new weapon ;)