Launchpad

Yes. Lion was coded by badly trained monkeys.

The only way of stopping this, for a while at least, is to clean everything from Launchpad. Paste this in Terminal:

When you've done this Launchpad will be empty, you'll have to add every application manually; you have to drag an app from your applications folder and drop it on your dock's Launchpad icon. The shifting will cease, until something causes it again.

You can simply select all of your applications and drop them on Launchpad, applications will be immediately categorized in Apple apps and apps you've installed, just like in iOS.