Arnold Kim at Mac Rumors:

Developers of these sandboxed applications must take special measures to break up their application into individual processes that only are able to do exactly what they need. Apple still allows user initiated actions to perform as expected and override the sandbox, but app-initiated actions in sandboxed applications will be restricted. This means that system wide file access and inter-app scripting and interactions will not be allowed.

Arnold wrote a great piece about Apple’s plans to sandbox apps. While it was supposed to happen this month, Apple put it off until 2012. It’s definitely worth a read.