Maybe you woke up from a long night and realize you've made a horrible mistake, posting dozens of embarrassing pictures (or worse) to Facebook. Maybe you've just decided that your five years on Facebook were experimental and you'd rather move on.

In either case, deleting more than a couple of posts or pictures can be a major pain. CNET's Elinor Mills recently wrote up a neat Android tool called Exfoliate that can scour your Facebook history and permanently delete some or all content. (iPhone users should see it come to the App Store soon.) Here's how to use it:

Install Exfoliate from the Android Market. Tell Exfoliate which data to delete. This is mostly straightforward, organized into time and content type. If things don't seem to work out the first time, try again with Background Override checked. If you're on a network you trust, you can uncheck Use Https Only to speed up the operation considerably. Sign in to Facebook. Exfoliate doesn't retain your log-in information. Authorize Exfoliate as a Facebook app. It needs a lot of permissions, as it has a lot of work to do. Now is your last chance to reconsider. Start Exfoliate by tapping the big button on the bottom of the screen. If you get cold feet or suddenly remember you need to save a pic or two, you may have a chance to stop some deletions. Exfoliate starts with the oldest data, so you can tap the cancel button and hope you caught it in time. If not, it's gone forever, so think carefully. This is a slow process. If you're deleting more than a few posts, you should probably leave it running and plugged in overnight.

That's it. As with any other app or service that makes irrevocable changes, you should think carefully before using it. For some users, though, Exfoliate could be a life-saver.

And hey, if you need to delete all those tweets while you;re at it, read Nicole Cozma's "How to Delete All Your Tweets".