It is impossible to upload two files if both have the first 50 chars and the suffix equal.

[do3cc]

If you upload two files with names like these:
looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong-1.jpg
looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong-2.jpg
Only one file would be uploaded, because the normalizer would create the same name for both of them, and both files are uploaded requests so there is no straightforward way to differentiate between a two file upload and an overwrite.
One could store the original long name in an annotation. But this could mean that people get confused why a fileupload sometimes generates a new file and sometimes not, because the information of the original long file name is lost.
maybe uploading images should not get trunctated at all when using collective.quickupload.
There is a mailing list discussion to this topic: http://sourceforge.net/mailarchive/forum.php?thread_name=CAFefbnHdyfbD%2B7xs69JUxkgMLr3gf1mNOUGYnB5Sudb-8NXYgg%40mail.gmail.com&forum_name=plone-users

[teschmitz]

I don't know where the cut-off point is but my longest file name is 65 char and it gets cut off by Quick Upload but not by Plone (manual upload).

For reasons of consistency, Quick Upload should apply the same max length as Plone.