This could be very funny. "Skip" - Andrew Pfister, the writer of 1up's GTA IV preview - has posted on Neogaf saying that the PS3 version of GTA IV features a five-minute mandatory install. Unsurprisingly, teh internets have gone grade A crackers for it.
We're also reliably informed this morning that the 360 version features an "optional install" as well. We'll drop Rockstar a note asking for confirmation.