I'm going to tell you about the most expensive assumption I ever made about people search engines. Two years ago, I was vetting a potential real estate partner who was supposed to bring $200,000 to a development project. Did my "thorough" background check using three different people search engines. Everything looked clean - no criminal record, solid address history, good business registrations. The guy seemed perfect. Until he disappeared with $23,000 of our development funds and I discovered that every single "fact" I'd found about him was either outdated, incomplete, or flat-out wrong. His "clean" criminal record? The conviction was...