Pretty amazing that sites with such high daily revenue (close to UK 7000/day, just for IE) either weren't testing their checkout process in IE or didn't ever wonder "gee why am I getting this 'insecure content' popup and how can it be fixed?".
As mentioned at the bottom of the article -- if you click "yes" on the popup -- then you only got the secure data -- and didn't get the analytics code. And that quite possible 70% of the users did just that.