Consider javax.media jai_core version 1.1.3 and the repositories central and open source geospatial foundation (at http://download.osgeo.org/webdav/geotools/)
Central has the POM and javadoc, while osgeo has the POM and jar file. My build required the jar file, but because central was listed first it wasn’t found. Rather confusing (jai_core was a transitive dependency, not one I had explicitly listed).
Can I suggest that there be some way of identifying this situation; when an artifact is not found continue search to see if it appears in another repository and at least say so if not actually use it.
In theory this also presents the possibility that there may be no suitable ordering of repositories. What is the best way of resolving such a situation? Perhaps create ones own repository containing the awkward artifacts and list that first.