Ask HN: What does it take to kill a business with strong network effects?

I read about network effects, monopolies a lot. How the holy grail of startups is a strong network effect and that will create a stronger moat every step you take. But there's also cases, such as Myspace losing to Facebook, where Myspace had incredible network effects but still fell. I haven't read anything on the other side of what it takes for them to fail. Is it the changing market, lack of innovation, I've even heard that Myspace load times were so slow that it gave FB an opening.