Is it currently possible / feasible / not crazy to implement a multiplayer game using javascript (+ flash perhaps) with code running entirely in client and a server only used to host a db, which the app/game connects to, to store / get relevant multiplayer information (player&opponents position in game world/items owned/hiscore) ?
If there is no server side code to validate the input received from the clients, the game will be prone to major security issues and everyone will be level 1million in no time.
Server-side code is mostly used to verify user input and format data received by a DB. You cannot do without it.