Tags are only useful if they're useful.
Sorry - I couldn't resist the circular reference there, but it's true. When adding a tag to a question I always think "Would there be some commonality between questions that have this tag?". Take for example the .net
ArgumentException, would there be value in two questions sharing this tag if they were, for example:
- I'm calling the
MessageBox.Show method and receiving an
- Creating a database connection throws an
In this example, apart from the obvious "one of the arguments you're passing is wrong", there's no commonality between the questions and the answers are likely to be specific to the circumstances and the values that the OP is passing to the method calls.
users could find possible causes for this specific exception
Many exceptions can have wildly varying causes, as I've suggested above, depending on context. So in short, would the tag add value to the site as a method of categorising questions and allowing users to view questions.
(I'm well aware that tags like c# are so generic as to contradict my argument above, but in the tag domain that exists for stackoverflow, tags such as c# are almost "super" tags and thus my argument doesn't apply)