slhck on error: I can't imagine anybody using this tag as a favorite.
slhck on failure: In fact, there's no follower for that tag either.
The amount of followers is in no way a motive to determine whether a tag is good, a tag is not a category.
You rather have to look whether it adds value when reading the question one-box and searching...
Other than that, burn it with fire!I think it's best that we retag them.
People should use more specific tags that describe what exactly is happening.
Is it hanging or crashing, does it timeout, does it give an error-message, a blank-screen perhaps?
At first I didn't see the vagueness behind failure, some arguments:
They do add value when searching...
For example, searching for power-supply + failure is different than searching for power-supply.
The former makes it easy to learn why power supplies fail and how they can be fixed, the latter just yields a lot of questions about power supplies while they are not all about failures.
They do add value when you see the question in a list...
It allows you to identify that the question is talking about a failure, the title doesn't always give that away.
Burning the tag takes this value away.
Splitting the tag yields too many new tags.
Also, you get long tag strings like power-supply power-supply-failure.