Though there is an option to "Share", it appears that you can only send it to other Spotify users. I suggest a method to be able to "send a song" via email to a friend. It would be something like "Have you heard this song?" with a link to that song on Spotify so that they can listen to it. It woould be a way to "drive" people to Spotify as well as a method to actually share songs one likes. Mke it so they can listen that song a time or two, after that they'd have to sign up.
For all referrals that come via this route for new paying subscribers I would get a percentage. Cha-ching baby, cha-ching!
Hello and thanks for your feedback!
A similar idea has also been suggested here:
Add your kudos and comments there please! 😉