and Google followed suite...
...with Chrome.
The folks at Google are simply preserving the pretence of online privacy - their entire business model revolves around monetising you and your actions on the web - so when they belatedly followed suite with an Incognito mode for Chrome guess what... they didn't make it the default either.
Hmmm... gotta wonder if those "representatives of advertisers" who argued strongly in the first place were Google and DoubleClick...
Of course with IE it's pretty easy to actually make inprivate the default mode - http://tinyurl.com/32nbz7a (a similar option exists for Chrome as well)
It would have been nicer to make this a user selectable default via GUI but there ya go.
Now of course there are some side effects of doing this... no more history, no more auto-login or sites remembering you ... and sites that rely on advertising revenue to stay in business (like, oh ... El Reg for instance) may find times getting a little tougher...
Sad how Microsoft innovate to protect users on the web - being the first to add a "private" mode like this - and then someone winds up a WSJ hack who bitches that they didn't go far enough