Where it becomes a problem for people who own a website is when this behavior causes additional support calls due to a more informative 404 page being masked.

It will likely result in incidences where support staff have a checklist of "do you have the Google Toolbar installed? Uninstall it first." However, I don't imagine there will be a ton of cases like this.

I do think it is a mistake that the Google Toolbar enables this by default. Taking this power away from the website owners is not good. And let's be honest, At least 50% of people who have the toolbar installed are not technically savvy and a good portion of them probably didn't even intend to install the software (it was bundled with another download, etc).

Also, I don't see a problem with the practice of putting sensitive data in GET variables if the website is protected by SSL - Am I missing something? Edit: Thanks for the reply aaco, those are both valid reasons and I appreciate the insight.