What happens when I share an iTunes Radio station I've created?
From the Apple website:


  With iTunes Radio, you can easily share stations via AirDrop, Mail, Messages, Twitter, and Facebook. The stations you share continue to change as you tweak the mix, so your friends can listen to music that adjusts with your evolving tastes. Show off your favorite stations, or tune in to your friends’ to hear what they’re into.


So, it appears to mean that they're getting a read-only instance of your station, that updates as you update it.