Why Does Cerebus Syndrome Happen?

There are a couple of different reasons why a webcomic can undergo Cerebus Syndrome [G]. The most common is that the author gets bored with writing what he or she has been, and he or she wants to write something different, more serious. Meaghan Quinn [G] has suggested [G]that in the webcomics world there is the feeling that each person should do one comic at a time, so instead of starting a second, more serious comic the author simply transforms their current strip into something different.

Another reason, as suggested by T Campbell [G], is that when cartoonists write a character day in and day out they tend to develop emotional ties to those characters and start to view them more as people and less as props for jokes. The author get attached, and the characters "become people we care about, and it gets a little harder to drop a safe on them, then point and laugh."

There is also a final, less artistically motivated answer. Comedy is hard. Sometimes drama is a fallback for when the jokes run out. Eric Burns [G] wrote that "It trie[s] to become dramatic -- in part because it [feels] drama is easier to pull off than humor." (Technically he wrote this in reference to the HBO series "First and Ten". However, this is because "First and Ten Syndrome" [G] is what he calls failed Cerebus Syndrome.)

We know why it happens, but how do we know if Cerebus Syndrome is successful or not?