Like with the Rift deal, the friend you refer will get 10% off their purchase ($20), bringing the Go price down to $179 for them. However, whereas with Rift you get $30 store credit in return, with Go you only get $20. This is likely due to the fact that games tend to be priced much lower on Go than Rift.
The referral program is still USA-only, and you can still only refer up to 3 friends, however those friends could refer more people themselves.
VR is more fun when your friends are in it with you. If you have a Go, the $20 off might just convince a friend to get one too. And when they do, you could have wizard duels with them in Wands, play Settlers of Catan in VR, battle in space in Anshar Online, or just watch videos together in Oculus Rooms.