I have gambled online for 5 years and have done *very* well. I have cashed money out several times and certainty of payment is not even an issue. Sportsbook . com is one of the books I use, and they are a publicly traded company in London. PinnacleSports is the other book I use, simply because they have the lowest 'juice' online and typically have very tight spreads. There are tons of people that 'beat Vegas' when it comes to sports gambling. There is an entire industry of these people in Vegas. They file tax returns as "KPG's" (known professional gamblers) and live in huge houses out there. My roommate in college made thousands of dollars his senior year by gambling online. I'll admit that some of it is luck, but the good players have a strategy and do considerable due diligence. For instance, last year I made a killing by gambling on NBA games by focusing my efforts on a niche markets -- Western Conference over/unders -- and studying those trends meticulously. My roommate in college made big money by focusing on college football. He would focus on home underdogs with the line under 7 points. There are a quite a few good strategies (betting against 'popular' teams like the Knicks, Jets, Lakers, taking the biggest and smallest lines every week, going with hot pitchers in baseball). The key is to find something you understand, research the heck out of it, and be consistent.
