On: RemoteStorage – An open protocol for per-user stor...

[needz]

Let's say the web app is a game and it keeps track of your high score when you play it, if the high score is stored somewhere you have complete control over, what's to stop someone from modifying that score? Substitute high score for any variable a server tracks about a user that isn't explicitly supplied by that user.

[eximius → needz]

The only way to prevent cheating in a game is to run the code on the server based on transmitted user actions.

Even with a server side DB, they could lie about their results or hack the game to do better.