I thought TIO sold a ton more. It's very deserving and should be 3x-platinum. Better than Blow though
It's because Blah Blah Blah was the 2nd single and had gained huge momentum from Tik Tok and she performed it on "Idol". Plus Take It Off was the 4th single.
I think the numbers for "Blah Blah Blah" and "Take It Off" are even more impressive when considering their run at radio, with overall peaks not surpassing 50 and 60 million A.I respectively. Had radio got behind both, I wouldn't be surprised if all of Ke$ha's singles were 3+ million sellers.