When there are no rules, the second law of thermodynamics will come into play and the entropy of the system will increase. One way in which entropy increases is that, without any restrictions on communications among subsystems, communication will occur in an unrestricted way...
from Code Complete, 2nd ed. by Steve McConnell
The above statement pertains, in context, to software development, yet "Twitter" is what popped into my mind when I read it.
As a medium, Twitter has the potential to be a time and attention suck, and can be a noisy place, but it doesn't have to be. I've managed to carve out my own little niche in Twitter that at least about 70% of the time seems worthwhile - ie. the signal-to-noise ratio is in signal's favor.
Twitter, and other social media tools, work best when they restrain least. But, without rules, how is it that Twitter does not become a toxic space bristling with the radiation of too much untrained communication and the subsequent death of thought?
Rules. Natural, self-selected rules we bring to the table. Take for instance, the two biggest self-selected "rules" for following/friending someone: location (is this person near me or in a place meaningful to me?) and interest (does this person exhibit a pattern of communicating info/thoughts that I can use/am inspired by/enjoy?)
A system that doesn't restrain users allows those users to restrain themselves along the lines of natural, meaningful patterns...
I recently commented not so eloquently on a blog post in defense of not following everyone who follows you. At the time, I was reaching, in part, for the idea I'm casting forth here - that rules form naturally in social media and are realized in trends in usage and communication based on human nature and human interest.
That's a positive. A system with rules, with thoroughfares and arteries, is a place where transport and communication, occurs. Unrestrained access and communication would result in a system without an organizing principle. And that way... that path pointing in every direction, would lead to the eventual death by heat-loss of the Twitterverse.