Every so often I just delete all my tweets. It's not automated, because I do it when I feel like it. The first ever twitter app I made was a delete-all-tweets app just for myself to use.

I purge content from my law firm website all the time.

I completely trash and start over my personal website every few years, too, and I've never kept anything in a purge. I have personal archives of it, and the various archiving sites have been snapshotting my stuff since 1999, so, meh, if anyone wants to find my old work product, there's a way, without me having to archive it all for the whole world for all eternity.

Sometimes it's nice to start over.

I like to purge my real life too. De-cluttering is fun. My zen would be to have nothing left.

Regarding link rot, the walled garden comment above/below is spot on. When you're dealing with a bunch of walled gardens, link rot is so far unavoidable.