I'm seeking a system for following (like used on Twitter.com) with the following parameters, or close to them, and I'm curious if anybody has a solution. I would like to avoid BuddyPress.
Basic PHP Code for Follow/Unfollow Links in WordPress Templates
A PHP code which generates a link that can be inserted on author pages to Follow/Unfollow a user. If the logged-in user is already following the author they are viewing, then the link will say "Unfollow". If the logged-in user is not following the author they are viewing, then the link will say "Follow" and allow them to follow the user.
A PHP Code Which Produces a List of All Authors Being Followed by Logged-in User
This would be useful to create a "Following" list so users have an easy place to view their author pages and un-follow them. Must be able to insert it on a page.
A PHP Code Which Produces a List of Users Following Logged-in User
This would be useful to create a list of "followers." Must be able to insert it on a page.
The Followed Authors Being Incorporated Into The Loop
I bet this would be the most practical way to incorporate posts from those being followed into a "stream," or loop of posts. I assume some function which pulled posts from followed authors may need to be created. Then posts could be grabbed in the normal fashion and the posts from authors being followed would be mixed in via the same method as all the other posts (for example, by date published).
Capacity/Scalability Concerns I do not just want a comma separated list of user_id fields in a wp_usermetavalue to be created as this would only work up to a certain number of followers - think scalability.