I really love the "follow back" thing on Amethyst. Exactly what was missing.

When totally random strangers I've never heard of before reply with something funny, interesting, or deeply twisted, I always click into their profile to see what else they're saying, having the "follow back" button is somehow much more inviting than separate "follows you" text and a normal "follow" button.

I've doubled the number of people I follow since this feature was introduced.