This is Paul Krugman's response to the Rogoff and Reinhart defense of their research that led to the conclusion that debt above 90% of GDP led to slow growth:

"OK, Reinhart and Rogoff have said their piece. I’d say that they’re still trying to have it both ways, on two fronts. They deny asserting that the debt-growth relationship is causal, but keep making statements that insinuate that it is. And they deny having been strong austerity advocates – but they were happy to bask in the celebrity that came with their adoption as austerian mascots, and never to my knowledge spoke out to condemn all the “eek! 90 percent!” rhetoric that was used to justify sharp austerity right now."

I like this response by the German economist Wolfgang Munchau in the Financial Times even better:

"The Harvard economists' tragedy is not the misuse of Microsoft Excel but the misuse of Microsoft PowerPoint"

Their well publicized Excel error produced bad arithmetic but the real damage was done by all of the presentations that they made which reinforced the 90% threshold message in their study.