The problem is, how many people have taken a real IQ test? I had to take one back in High School for some reason, and it was over the course of three days. Pattern recognition, spacial perception, memory tests like reciting back progressively longer strings of numbers in reverse order... Followed by a fairly difficult multiple choice test on various subjects that took several hours to complete.
It was fun, I'd like to do it again and see how difficult it is these days. I scored above average, but the actual score is fairly irrelevant unless someone else has taken the same test.
And then there's the online 100 question multiple choice "tests".