You are certainly right, it's just that i have a view from a different angle at it.
The files on my ownCloud or other webDav storage are owned by me and not shared. That should be garantued by the credentials needed to access them. I can not see any special legal issues here besides the general problem of multiple copies.
The technical availability definetely is a problem. But not for me. I use Cross DJ as a replacement for winamp+pacemaker. Instead of carrying a laptop arround i have it handy ;-) I very rarely use the mixing abilities, sorry to say that
I use it merely for playing dance sport music (standard/latin) and love the timestretching for training reasons. When the network fails i still have enough fallback.
Anyway, i guess i'm one of the few who'ld benefit from that.