> Maybe shipping your software with a 'developer mode' toggle is the right way to do it!

Well, Firefox's incognito mode goes in the right direction. It's nice to be able to put the browser in a mode where it does the right thing without prompting (where right = respects the user's privacy by default). It would be even better if incognito mode was the default and instead users had to go out of their way to put their browser into "unsafe mode" in order to expose all these nasty bits to web sites.