First thought: no control group.
Alternate hypotheses not considered at all, which is really a whole category of problems/thoughts.
Didn't seem to care that they were measuring different things in adults and kids.
As it is, the article is spending about half of its two pages just to say "the way we define 'gifted' is totally different in kids and adults, and so people who are in one group aren't necessarily in the other."
“Sometimes,” says Dr. Freeman, sitting in her airy office in central London, with toys on the floor and copies of her 17 books on the shelf, “those with extremely high IQ don't bother to use it.” (article) Your thoughts on that issue?