I doubt it.
Even those of us who might be considered "in the know" might be surprised. For example - Do you think you're only sending 140 characters (or less) when you post those tweets on Twitter? A quick read over at RRW proves otherwise.
If that's not surprising enough for you, go install Ghostery and spend a few minutes on your favorite websites. If nothing else you might find the sheer number of advertising platforms (an entire industry dependent on hidden text!) out there a little unsettling.
Title: Apparently you don't see it.
Snarky: What's hidden text?