Functionality on Steroids

At what point does an informational tool become so overwrought that it becomes something entirely different from its base form?

A standard street sign has a known function and simple premises and affordances. It is intended to provide context within a given city. The example above, while providing some local context, is meant to set the reader within a global context. It is not "usable", but it does provide a function.

Overwrought software is nearly always frustrating. Are there cases where it begins to fill a different purpose altogether from what the designers intend? Can such products have repeat usefulness?