Remember to read the intro.
I don't remember where I first heard about the circuit breaker pattern but I had seen it a few times in a few different forms under different names. Over time I have come to believe that the original approach described to me might not be the most appropriate.
A while back I needed a way to simply post tweets from PHP. To my disappointment most examples I found were about reading tweets or required a bunch of PHP modules I did not have the opportunity to use on the server where the script was going to run. So I had to do some work.
Probably one of the most common tight couplings I see is a dependency on system time, i.e. using DateTime.Now or DateTime.UtcNow directly in your code without any abstraction around it. A tight coupling that typically leads to very complex and fragile tests when trying to ad test coverage.