The article you link to and quote, while saying grades are less important than Google thought, goes on to say that progressive Google after doing this study and at least partially implementing its new system "Last week...hired 6 people who had a below 3.0 GPA." 6 out of an estimated 200 weekly hires. That's a far far cry from D student = A student and nobody can tell the difference. Also, all of the direct quotations from Google people in the article talk about years spent in academia, degrees like doctorates, and interviews being the poor predictors. Some of the best programmers I know dropped out of high school. Doesn't mean I couldn't tell apart a room of A students from D students or that I couldn't use the A students better for many jobs I might need to fill.
There are only a handful of studies because it's considered kind of a dumb question to ask. But Alfie Kohn references some of them in his books, I think in What Does It Mean To Be Well Educated? But the ones that exist consistently show the same thing.
This includes the huge internal study that Google HR did:
"Unfortunately, most of the academic research suggests that the factors Google has put the most weight on — grades and interviews — are not an especially reliable way of hiring good people."
"When all this was completed, Dr. Carlisle set about analyzing the two million data points the survey collected. Among the first results was confirmation that Google’s obsession with academic performance was not always correlated with success at the company."
http://www.nytimes.com/2007/01/03/technology/03google.html?e...