The act of killing a
trademark by using it as a common
noun rather than a proper
adjective.
Genericide is a company's reward for being too successful at promoting its brand. Once a mark no longer identifies a specific source, but instead the genus of goods or services, it no longer performs the function of a trademark -- so anyone is entitled to use the term. Famous trademarks killed by genericide include Thermos vacuum bottles and Aspirin pain killer.
Kleenex and Xerox are tottering on the brink of genericide. When was the last time you asked for a "facial tissue"? To try to avoid this miserable fate, Xerox advertises from time to time with the tagline: "You can't Xerox a Xerox on a Xerox. But we don't mind at all if you copy a copy on a Xerox copier."