Observer Effect: Acknowledgment that the act of observing will make changes in the phenomenon being observed.
So yesterday I read the latest XKCD.
Like the typical Internet geek who reads XKCD, I immediately open Google and search for the exact phrase "Died in a Blogging Accident." Of course, I don't know if the answer was ever "2," but now the search yields 7,900 results, most of which seem to refer to this XKCD cartoon. And now I have added one more.
Update: One suspects that the number was always greater than "2", since filtering out responses that include "XKCD" still yields over 6000 results.