Either Google is onto something - a new experiment perhaps or a hack- or entire web is harmful and full of malicious content according to Google. The image shows the lame search for "MSN". However, if you click the link, rather any link on search engine result page, this is the screen that welcomes you: "Warning - visiting this web site may harm your computer."
Do you really think we cannot trust the world wide web any more? Do children need protection to such an extent? I do not know, you decide. :-)