A second problem is the format of tags isn't standardized. This means that issues such as how white space is handled, which characters are legal, and which characters have special meanings and what those meanings are go undefined.

The third and perhaps biggest problem is the overuse of tagging. How often have you seen a blog item with a list of tags almost as long as the item itself? This is a direct result of the optimism of tag authors -- they want to cover all of the bases so their content can be easily found. Thus, if "wind" is a tag, they will often include "windy", "winds", "gusty", and every other synonym and related term to ensure that the item can be found no matter what. Tag lists are often more like reading a thesaurus.