Unfortunately, Time Machine has a serious problem: there is no way (that I can find) to remove a file from a Time Machine backup. This is a pretty glaring omission. After all, Leopard has a “secure empty trash” feature that lets you throw away files so that they can’t be recovered with forensic tools. What’s the point of erasing a file on the hard drive and then overwriting the disk sectors seven times if Leopard is going to keep a copy of the file in the Time Machine backup?

Agreed. It seems like while handy to have backups, sometimes you just want a file totally gone. Though, I store anything sensitive (like financial items, etc.) on an encrypted disk image. However, if Time Machine is backing things up every hour – it could grab such a file before one has time to copy to a secure disk image. So, while you can turn Time Machine off for specific folders, etc – it’d still be nice to have some way to obliterate all copies of a file from the past, as well as the future.

You can delete all backups though I doubt they’re done “securely” with overwrites. See below.