Due to the extreme amount of time required to repopulate a workspace, we run our Hudson build without doing a clean of the workspace with each build. Thus in the normal case, we have a build run once an hour, it downloads all changed files, and then it does the build.

But if a file in the workspace is missing or corrupt, it doesn't attempt to re-download the file. Determining if the file is corrupt might be tricky (I suppose one might store an MD5 sum in the local database for the workspace). But when you have a file that is missing from the workspace, it ought to be a no-brainer that the SCM plugin should download a new copy of the file.

I ran across this because I used this bug/feature as a workaround for this issue:
https://issues.jenkins-ci.org/browse/JENKINS-13220