I think you should pivot. What your site allows users to do is one of the many things people can already do on Twitter and Facebook much simpler, without the u

I think you should pivot. What your site allows users to do is one of the many things people can already do on Twitter and Facebook much simpler, without the use of dropdowns, just by typing whatever they feel like into the share box. You're adding very little value (if any), but want to create a separate walled garden against one thousand pound gorillas mentioned above. In fact you're subtracting value because users aren't on Twitter or Facebook where their friends actually see their shares.