" + " = "Like"
" - " = "Don't like"
" : " = "Follow"

A "Neutral" button is completely superfluous. Why? Because you don't like, dislike, or follow on something you feel neutral about. Indifference ("neutral") requires no action, therefore should require no button.

Why should " : " be used as a symbol for "Follow"?

Symbolically the " : " is two points (dots). One above (or see more positive) relative to the other. A person may be indifferent about a topic, blog, forum, post, picture, but still want to "Follow" both the positive and negative things about it in the future (and past).

Mathematically* the " : " symbol is used as part of a set-builder** notation "...stating the [positive, negative, and neutral comments] properties that its members (users) must satisfy." A set is a collection of elements or members.**

Grammatically a " : " is used in citing references at a local, as opposed to specific street address or broad state or country, level of where and when something is published. As well as when a list of examples are to follow a point as listed below:

- You are reading this point you are following what I listed after the " : "
- If you've read this far then you may agree that the " : " may be more intuitive of a character to symbolize "Follow" that you had originally thought. ;-)

I believe a slider would just ad another element of complexity to something that should be kept very simple.

Someone could both "Like" a topic and also "Follow":

Example "+:Kittens" wold be to like and follow Kittens.
or

Someone could both "Don't like" (work with me here) and "Follow" a topic:

Example "-:Murder" would be to not like or be a fan of Murder, but want to follow the topic.

Finally, a " : " could follow both sides, positive and negative, of an item, topic, etc. without having to
disclose whether or not you like or don't like it:

Example ":abortion" would mean to follow something you regardless of how you feel about it personally.

Feedback is welcome. Please note I am not a premium member and do enjoy contributing to the topics so please do not close the discussions off to just premium members if you found my input helpful.

* Mathematical symbols: http://en.wikipedia.org/wiki/List_of_mathematical_symbols
**Set-builder notation: http://en.wikipedia.org/wiki/List_of_mathematical_symbols
*** References (Citations): library.rit.edu/pubs/guides/mla.pdf