Google desktop search
I bought Johnny Longs book Google Hacking for penetration testers and I have also talked in the past about google hacking and also about the security concerns raised about having the google desktop search engine as it can find vulnerabilities and security risks on your own machine. I made some posts here about this recently, these include "Google hacking and reverse engineering Java", "Google hacking search string database", "Google hacking is on the up!" and "Bruce Schneier talks about google desktop search security"