For some years now, I'm waiting for Subversion to feature a "delete permanently" (obliterate) function. I hesitate to make the transition to Subversion (coming from Visual SourceSafe :p), because I think this is an essential feature, as otherwise I'd expect the repository to grow unstopably. However, for one reason or the other, the feature gets postponed over and over again. So I begin wondering if there is some other feature or workaround which makes the obliterate function dispensable.

What do you do when you want to shrink the SVN central repository?

Example 1: I check in a large third party library, and after a few weeks I realize it is not suited for my needs. I don't want that to store and backup that large amount of data forever.

Example 2: I have 10 versions of 10 big third party libraries in the repository, but I only use the latest versions.

Example 3: I accidentally checked in sensitive information (as suggested by John).

Example 4: I accidentally checked in some big files that were never meant to be put in the repository.