Who Supervises A Witness?

I have just made a whole month since joining Steemit and it has been a great first month. In that time I have learned a few things, not only by trying to use what sense I was gifted with, but also by learning from those who take their time to give out great information.

These are things I've learned about:

(1) Posting

(2) Using (or not ) using bots

(3) Up voting

(4)Resteeming

and

(5) Witnesses.

I've learned about other things as well, such as what rooms to join on Discord and other sites like Steemit Chat. The one that I've recently learned something about which I didn't know, is the Witness category. Although I have voted for witnesses, I didn't know that some of them aren't actually active. I found this out from @netuoso who wrote this greatly informative post. In it he directs his readers/followers (not the same thing) to a page where one can check to see if the witnesses we voted for are actually active. I have seen his list and while I did delete one or two, I'm satisfied with my choices. There were two that were inactive a bit but they help the community out a great deal. I kept them. I'll need some more info before I proceed.

Here is the reason for this post. How are witnesses being tracked, or rather by whom? What is done as a general consensus to a witness who isn't actively working or missing blocks? What effect does this have on the blockchain? How does this affect events like the recent low bandwidth issues that we experienced? These are just some of the questions I hope will be addressed, without having to wait for the next Hard Fork. If any of you have answers, be it my buddy @good-karma or @blueorgy or someone else, please let me know below. I'd appreciate your input.