Media Molecule boss David Smith's just confirmed that LittleBigPlanet will come with a mandatory install, but that it won't be as heavy as many other PS3 titles.
"The game is designed to be fairly lightweight, to make the sharing of new content easier," he said. "Our levels squidge down into really tiny files, which means that when the community makes new ones, they'll download quickly. The HD install is perhaps around a gig. Perhaps more or less. It's not finalised yet."
The news comes from an ongoing Live interview with the dev chief on Eurogamer.