If you manage to get your hands on a copy of Demon's Souls early, good for you. However, publisher Atlus says no servers will come online until its release date of Oct. 6 (Tuesday).
You may still play it singleplayer, but if you try to connect to a North American server before then, you'll get a PSN error. Atlus shares this information in the interest of quelling "worry, panic, confusion, mass hysteria, riots in the streets, armaggeddons, etc." And in the name of peace for all mankind.
Demon's Souls Servers Won't Go Up Until Launch [1Up via Destructoid]