This website is a great example of the challenges with being data-driven. It leads to a conclusion which is terribly flawed because of a failure to account for relevant nuance in the data.

C# is definitely not C++ or C. It would be better to lump it with Java.

But how many developers are now going to walk away thinking they should bone up on C since there are apparently so many positions out there for it?

And how many other statistics out there are similarly flawed? How much of our day-to-day off-the-cuff knowledge is based on poor data entry?