Can you reinstall OS X on a FileVault 2-encrypted drive?
If you don't care about the data, it's pretty standard (almost doesn't quality as "cli-fu" even); from Recovery HD, you can do it all in Terminal (Utilities > Terminal)

First, do a diskutil cs list to see the CoreStorage information on the volume. Grab the longish UUID of the Logical Volume Group you want to nuke (typically near the top of the output; scroll up). Now, diskutil cs delete UUID (where UUID is the LVG's UUID). Requires no knowledge of the key or an authorized user. Just blows the volume away. 

Again, if you don't care about the data. A completely legitimate example of this is a laptop my predecessor used to test FileVault 2. Didn't use an Institutional key or a local one he left where anybody could find it, and his account was the only authorized user.