

If you wanted to compress files before sending them to another drive, or over a network, or by email, then Compact wouldn't actually help at all because the files have to get uncompressed whenever they're accessed, especially before sending them anywhere. Turning this off has to be done by booting into the recovery console, if my memory serves me correctly, and it's a real nuisance. Use this command is when they're removing disk compression because someone turned it on to save space. Very bad! It makes your computer very slow and is quite difficult to undo. It enables disk compression which is a total no-no. There are additional concerns with the Compact command.

I fully agree that Compact is not the answer.
