When I dowload the latest Force.com IDE for Mac OS, and I try to extract the .tgz file using Archive Utility, I get an error:

Unable to expand "force.com-ide-installer-macosx.tgz" into "Downloads". (Error 1 – Operation not permitted.)

Doing tar -zvzf force.com-ide-installer-macosx.tgz in the Terminal results in:

force.com-ide-installer-macosx/configuration/install-content.bin: (Empty error message)
tar: Error exit delayed from previous errors.

What's up with that?