> I believe there was a $2b writedown on the Surface RT, as well as $7b + on the botched Nokia acquisition. Those are failures you can attribute actual dollar figures to.

You can add $1 billion for the discontinued in 48 days https://en.wikipedia.org/wiki/Microsoft_Kin Kin social networking phone, in which they also scored an own goal against their cloud offerings by trashing the database running their purchased userbase: https://en.wikipedia.org/wiki/Microsoft_data_loss_2009

The total losses, official or not, have got to run into the tens of millions.