Although this is a little late, I just wanted to share some follow-up information regarding the Cognitive Group meeting from November 2nd. Specifically, we discussed the myth regarding the idea that the meaning of words should not be allowed to change. Instead, we talked about the flexibility that is inherent in language and how change is an inevitable outcome for any viable language. Although common ground (and common meaning) is important for successful communication, language must also be able to grow and adapt to meet the needs of its users. Most of the time, change in language happens slowly enough that we don't notice it; other times, language change comes blazing in with a bang in the forms of new slang (although often it seems these words can also die a sudden death). Overall, however, the community that uses the language does a pretty good job in understanding one another.
To learn more about the study of words, see this TED Talk by Erin McKean on Redefining the dictionary. You can also see Erin talk more about words during her Google talk Verbatim.
Thanks, Lucas, for these great references!