Lion kills application behind the scene, how to put application on a do not kill list? I am encountering an irritating feature of Lion.

Say I spend 30 minutes in XCode, then I go to iChat to talk to my girlfriend for 5 minutes, then I switch to Safari to check StackExchange, gmail, and whatever else I might want to check.

Then I switch to Safari where I run another set of pages. For 5 or 10 seconds, the app resumes with beachball. This is annoying as hell (switch appnames around, they behave the same). 

How can I prevent this from happening at all (unlikely) or at least mitigate it by making a list of apps that are not allowed to go into silently-killed mode?
You can't. Check out this thread on the Apple discussion forum. You can also read this article from TUAW.