A man, ravenous with hunger, walks into a kind group of villagers who offer the poor starving man a sandwich. The starving man takes the sandwich willingly and proceeds to eat it. However, after a few bites, the man finds the sandwich not to his liking and instead of courteously returning it, he throws it on the ground and then curses the kind villagers that they would give him such a disagreeable meal, free though it may be.
If you're thinking that this hungry man is a jerk and should just be appreciative of the free work and help of others, then you got the gist.
This is a work in progress, people... and a much needed work at that. FTP, stable and functional though it may be, is robust only when compared to the internet circa 1990. In the year 2012, FTP - though useful - is not a viable framework for file sharing. It doesn't swarm, it doesn't support a decentralized network model, and the way most people will set it up, it is not secure.
I am not in any way affiliated or related to the authors and programmers of RetroShare or the project (just a user) and appreciate that they are trying to create a private peer to peer sharing framework for our benefit. I hope that they continue their development and that one day - as another poster mentioned - it is as popular and stable as the current crop of BT programs.