Specificity in tagging
The line in the sand is a little vague, but I think we should avoid adding source tags for overly specific things, when a more broad tag would suffice.
If the source in question is commonly used on it's own, then giving it's own more specific tag makes sense. Pizzaday.wmv is a good example. It has it's own tag separate from Rocco Botte and that is understandable.
However, in cases where the more specific tag is not commonly used on it's own, it should be avoided. As a real example, this SimpleFlips video had it's own tag, which seems a bit superfluous to me as it is not a source that is commonly used separate from SimpleFlips in works.
Obviously, having things be more specific can be helpful to the sites goals, but if things are too specific it will lead to tags being forgotten, and as such not added to works properly. We should try and strike a balance between having specific tags for common YTPMV/otoMAD fixtures, while not going so overly specific.
This is just my opinion, of course. As I said, there are no guidelines about this, but I think it'd be nice to keep in mind for future tagging.