What brought a Learjet 60 down in Palm Beach County, Florida, is still an open question for investigators. The jet had left Austin headed for the Bahamas, and all nine aboard died, among them Adam Robinson, 44, a Texas founder behind http://Retention.com and GetEmails. Also on the flight: his wife Helen, two young children, a nanny, two friends, and the crew, pilot Jeff Gregory with co-pilot Nathalia Gadelha Filgueiras. The career detail is the strange part. Robinson's software surfaced email addresses for companies from people who browsed a site and slipped away without a form, and the notion that this is illegal in the US is a misconception that apparently travels widely.