It requires JavaScript, so it may not work depending on the security settings. In Internet Explorer, it triggers a security warning.
To be honest, if you're using IE and if you're going for the paranoia security settings, then you should already know this and that's not a problem SFML has to take into consideration. You just
can't go and support any darn browser that has ever existed with any kind of possible addons and settings combination. Or do we also have to make sure that it renders well in Lynx or Netscape?
There are also many people out there that block JavaScript, but is it now SFML's job to provide a non JavaScript-backed search engine, just so they don't have to activate JavaScript?
I don't think so.