It was always going to be a struggle squeezing everything from the PS3 version of LBP into the PSP version. Something had to give. Turns out that something is multiplayer.
"The one thing we've lost is multiplayer," Sony's Mark Green told Eurogamer. "You've got full physics systems, you got full create mode, you've got all the aspects of LittleBigPlanet - you can upload, download, ad-hoc share with people - but we haven't got multiplayer".
"It's a trade-off", he elaborates. "The system is physically capable of doing multiplayer, but perhaps not with the full physics system. On the technical side of things you lose a third of the processing power or a third of the system memory just to do multiplayer at all. With those limitations we couldn't achieve it."
Hey, fine by us. Couldn't really see multiplayer being as viable on the PSP anyway.
No multiplayer in LittleBigPlanet PSP [Eurogamer]