2009/4/7 K. Peachey p858snake@yahoo.com.au:
Currently undos, so frequent on wikis, just blindly create a duplicate row instead of checking if the old one could be reused, https://bugzilla.wikimedia.org/show_bug.cgi?id=18333 . Maybe some hardware savings could even be achieved.
From my understanding they have to be kept within the system to keep us within the GFDL licenseing terms.
The text doesn't need to be stored twice, though, just a note that it is the same text. However, I believe the Wikipedia databases have the text compressed, so that is effectively what happens already.