Ask HN: Userspace networking parallels to Keybase's use of FUSE

Keybase's recently-announced KB file system is an innovative use of FUSE (userspace file system).

What are some possible innovative uses of userspace networking (Netmap, DPDK, Snabb Switch, NUSE, etc.)? Is performance the primary gain, or are there other advantages or innovations that could parallel's Keybase's creative use of FUSE?