SUN VALLEY, Idaho (AP) -- Swindlers have stepped up their effort to fleece millions of dollars from online advertisers who use lucrative marketing networks run by Google Inc. and Yahoo Inc., according to a quarterly report to be released Monday. The sales referrals generated by clicks on the brief advertising links popularized by the two Internet powerhouses are a sham 14.1 percent of the time, based on information collected from 1,300 online marketers. That's up from a click fraud rate of 13.7 percent three months ago, according to Click Forensics, a San Antonio-based consulting service that compiles the index. The...