There are three main benefits to increasing the file size limit from the current 20MB to 40MB.
- Audio files - Spoken Wikipedia - avoid having to split one article into 2 sound files.
- Video - easily passes the 20mb limit quickly.
- DJVU files for Wikisource - avoid having to split one book into multiple files. See e.g. http://en.wikisource.org/wiki/Sacred_Books_of_the_East - some of the listed texts are currently hosted on the Internet Archive, but can't be uploaded at Commons without splitting or fiddling around with downsampling.
Last major discussion about it that I am aware of is http://lists.wikimedia.org/pipermail/wikitech-l/2007-October/034344.html
Tim: "My tentative answer would be that I don't think we're very far ahead of
the growth curve on storage. I don't know how expensive it will be or
whether we will be able to deploy new hardware fast enough. Our record for
deployment of storage hardware has been pretty poor."
So whenever that changes, please reconsider this bug.