This message was posted on behalf of Intel Corporation
“The USB_VBUS signal should be applied to pin 20. This signal is only used to alert the Intel® Edison that it has been connected to a host port.”
This means you don’t need it if the Edison is working as a host mode, even though, in this thread: https://communities.intel.com/thread/57510 there are some reports of issues when the VBUS is high.
Certainly, it should be connected.
You must supply 5V to it in the host mode. Peripheral devices will receive power through it.
Sorry, not very clear. I mean the VBUS_USB pin on the edison itself as described by Charlie above. I believe he has the right of it. In host mode, this pin needn't be connected at all.