[bt sync used as a social network]

There is this: vole.cc which seems like what you're talking about. Looks promising if they can keep up with it. 

[iOS sync all photos included imported]

I can second this thought of picking particular albums to upload instead of just camera roll.

Actually this is somewhat on the behalf of a school district looking to use iPads in photography class (backing up to class computer) and the publications group (yearbook stuff) for same reason.

[Sync between two USB Drives on Same PC]

This is easy. Make new user. Login. Run BTSync. You have 2 BTSyncs running in separate processes, now you can emulate syncing of 2 hosts.

 

Just checked it worked very well on Windows 7.

Can confim this as well.

 

The other option is if your computer is beefy enough, run a small virtual machine. Attach one drive to the VM and one to the real machine.

I use it this way because I normally have a VM up anyway. Obviously this isn't a solution for everyone, just an option.