Ben Edelman at the excellent Berkman Center for the Internet and Society has done a quick and dirty Empirical Analysis of Google SafeSearch which indicates (not surprisingly) that using “Safe Search” to prevent unwanted porn links coming up on your kids’ searches also accidentally (I have to assume) hides pages by the US Congress, NASA’s shuttle programme and numerous entries from Grolier Encyclopedia. It also lets through “numerous sites with sexually-explicit content in response to searches that unambiguously seek such materials, even as the majority of sexually-explicit content does seem to be blocked.”
As Edelman points out, if you use SafeSearch you will never know what was blocked or even how much was blocked so you can’t judge how much is missing. There is also no formal mechanism for warning organizations they have been blocked and no appeals process if they have been improperly blocked.
Yet more evidence (if more were needed) for my concern that search engines have a lot of tacit and even unintended power without a great deal of scrutiny.