It's a given that there are still a lot of people oblivious to Twitter. Car mechanics ... doctors ... landscape gardeners. Just by the nature of their work, they probably haven't been exposed to it, or needed it for their daily tasks. Just like they use tools that I've never had to learn about.
The clue that Twitter is becoming mainstream is when you see its slang being used elsewhere. For example, notice how bloggers and commentators now use @ when they reply to someone in the comments section? If you were starting to monitor blogs for the first time, you'd wonder what the @ stood for. Twitter users are familiar with it so are already "speaking the language."
I can't recall another social media tool that crossed over so easily. Tweet me @johncarson if you can suggest some, thanks.
~ John Carson, Senior Digital Media Specialist, GCI Canada