Allow me to clarify. When you hash a file, a time stamp is generated "[21:42:52] Finished hashing: ...\SharedFiles\Blablabla" in the notification bar below. I think that a date could be added to that. The result is stored in the hash file or wherever this data gets stored (filelist.xml). You do have a point regarding the growth of that file, but I'm sure you folks can figure out something ;-)
Take that time/date stamp and include it in a column when you are viewing someone's filelist so that you can arrange the files by time/date and see what's new. If it's too difficult to include a similar column in search then forget search.... just focus on the fileslist view.
I'm having high hopes for this!
PS: What tools/libraries do I need to tinker with the source code of Apex? I'd like to assess the feasibility of this suggestion.