Even if it wasn't a hoax, it's still fairly meaningless. It doesn't seem unlikely that more intelligent users would be more likely to look for other options rather than using the OS-provided default. For the sake of illustration lets simplify: Users with an IQ over 100 look for alternatives, below 100 and they do not. Even if 80% of the higher IQ users ultimately choose Internet Explorer (which would indicate that it is very high quality), there would be a very significant difference of average IQ between IE users and users of other browsers.

I also find it very distressing that the BBC, CNN, and a whole slew of other outlets all reported this without carrying out the kind of basic checks I do when presented with new information, and I'm not a reporter!