Knocking an Established Site/Forum out of the Google Index

Shawn Hogan:
"If someone wants to have a stab at knocking www.digitalpoint.com or forums.digitalpoint.com out of the index, be my guest. It would be an interesting experiment to see if it can actually be done or not."

The above quoted from this thread.

Now with DP being one of my favorite forums I would hate to see it get knocked out of the Google index, but I agree with Shawn that it would be an interesting experiment to see if it could be done. DP, the forum and the site, are what I would consider very "established". If it is possible, what does this say about the state of search?

Is it possible to knock a large established site out of the Google index? I guess we'll have to wait and see.