The PlayStation 3 version of Prototype has a nasty little bug that may affect some users as they try to install the game. The PS3 may claim it does not have enough free space on the hard drive even if it does, but it can be solved by a goofy workaround.
By changing the amount of free space on your hard drive by at least 700MB, the game will complete its mandatory install and you can begin slicing people open on the streets of NYC. Want a suggestion on how to do this? Delete or download a game demo.
Activision has stated that a patch will be released over PSN shortly. Unfortunately, this workaround is necessary until then if you experience the bug because the installation is mandatory. PS3 owners might recall the same bug with Ratchet & Clank Future: Tools of Destruction.
In other news, I conducted the optional install of Prototype on the Xbox 360 last night and was playing it so much that I forgot to eat dinner. True story.