14 DAY TRIAL // It is a serious breach of the 'do no evil' honor code that Google prided on. And it's not the first time this is happening, either, Google has on the off occasion provided third parties with information on people that were later convicted because of it. As natural as it may seem (if they were convicted, they must have done something wrong), the Mountain View-based company acted as such without being forced by a court order, no matter what the charges.
The DigitalPoint forums are hosting a lively debate whether Google taking over 404 pages as shown in the picture on the left is a good thing or a bad thing. I'm just kidding, but there are some people who are saying that the Mountain View-based company couldn't have done this unless there was some coding error on the behalf of the site owner, who set the 404 Error page to redirect to their index. In other words, give a Status-Code 404 for the page.
This is not Google being helpful with their hints as to what the user's next action could be and the Google search box, this is hijacking. If you buy a domain and want to have a dozen 404s they should let you do so, not change what the webmaster (you) decides to show to the visitors and instead plaster their logo all over the page.
Apparently, this only happens to people who have the latest beta release of the Google Toolbar and it only replaces default error pages. Should the webmaster choose to change anything about it, put in a smiley face or anything else, it will remain the way it was created with no Google interference.
Bring on the tar and feathers, anti-Googlers, this is your chance at some good poking your nemesis in the eye. If you don't fall under that category, just kick back and customize your 404s, if you really want to.