Recursive folder upload has always been a feature in Rad Upload. This is something that other HTTP upload systems cannot do. Many clients who used this features made support requests asking for help on recreating the user's folder tree at the server.
In other words our clients wanted to know what may have been the 'top node' when a user dragged and dropped a folder into the applet. This information could be determined easily in three different ways. The first being to assume that the first entry in the array will have the top node as it folder path. So if you stripped out the filename section from the full path name that's passed by the applet you get the top node.
In the second approach you get the shortest path name and strip out the filename section you end up wtih the top node once again. Third alternative is to count the number of file separators in the pathnames and use that as the top node.
None of these methods require more than half a dozen lines of code but still we decided to make it easier for our customers, after all the customer is the king.