There is no way that building an ISO can be seen as equivalent to drag and drop.
Folks, drag and drop is something I don't see ever happening. Think about what a VM does.. it emulates hardware at a very low level. So suppose the low level mouse code sees (left click, mouse wiggle) somewhere on the VM screen, followed by (left release) somewhere on the host screen - how on earth does it know that this actually means to copy "guest\C:\Document and Settings\My Magnum Opus.doc" to "host\D:\FutureGlory"? And what mechanism exists to do the copy, that both OS understand? The drag and drop operation requires a far more intimate interaction and understanding of the context certainly with guests than I think VirtualBox - or any other VM platform - is capable of. Now if someone is claiming that VMWare or whatever already does this then I'd be fascinated to learn how, because I don't see a practical way. [ And - I'm also fed up reading ignoramuses with absolutely no technical understanding mention how surprised they are that this isn't done already. A lot of stuff in life must surprise them. ]
What might be possible is a 2-stage process. Drag to a toolbar icon within the guest. Followed by drag from a host widget to a destination. This would still require that handlers be written for every supported host and every supported guest. Even with the compromise, it's a lot of work... for a minor convenience. [ edit ] this amounts to an automatically created shared folder.
 And oh yeah... a one-stage drag and drop feature also implies a bidirectional conduit between hosts and guests in which files can be opened, copied, read and written behind your back even when there is no network connection established - and this is not even contained within particular folders. This has obvious malware implications.