Steps to reproduce:
*Start upload wizard
*Upload 2 files
*Give them the same name on the describe step
*Upload wizard should give an error to the user, as this is almost certainly not what the user meant to do. Presumably this was a typo on the part of the user, and they did not mean for the files to have same title (or didn't realize there is 1:1 relation of titles to files. In any case, if user is uploading 2 files at the same time, they probably want them to be separate files.
*Upload wizard uploads the first file, and then uploads the second file over top of the first.
Additional actual behaviour:
*Race conditions galore in the backend cause bad things to happen, and data-loss on one of the files. See bug 54736. However, even if that didn't happen, this is still a behaviour of upload wizard that I think should be fixed.