Chapman - 10:50 pm on Mar 7, 2013 (gmt 0)
I find all the above comments to be quite enlightening, however, my results after disabling "Interest-based Ads" via the control panel appear to be different than what others have described.
It's true that some IBAs continue to be shown on my sites but the number is significantly lower. Targeting type reports, after disabling IBAs, do show that "something" in that category is still being shown but the numbers are 20% of when they're enabled - sometimes even as low as 10%.
An additional oddity I see is that the click value of the IBAs still being shown while they are disabled is just about double of that when they are enabled.
There is a whole lot of voodoo connected to that control panel option, I believe, but having it switched off is working for me!