It's easy to imagine reasons. A lazy assistant who's supposed to go through 13,488 filled-out forms decides to count 1,000 of them and then fabricate the rest so they can spend the week watching soccer online instead? Or an employee lost the data on which form results were associated with which condition, and they might get fired or not get promoted if caught, so they made it up? And so forth.

And metadata as you've described it doesn't sem like a smoking gun either. It's easy enough to imagine Ariely created an otherwise empty Excel sheet in the column format he wanted them to insert data into, e-mailed it to them, and got it back with their results. Or he just copied their Excel results into a spreadsheet of his own that already had other tabs, or similar.

I'm not saying Ariely didn't do it or did do it, I'm just wondering if there's an actual smoking gun here, or if it's just accusations but we'll never really know.