Just to complete Adrian's view, I'd add providers that only support obsolete versions and are unlikely to be updated.
In that case, I would definitely prefer to simply remove them and e.g. have a Wiki page listing the providers that are no longer in the repo, together with the commit which removed them.
I guess that's not too different from an "attic repo" ;-) I just don't fancy the idea of a jclouds-* repo with code that may not build and almost certainly doesn't work.
ap
