I have been playing offshore for 7 years....and have been stiffed twice......by Allworld and BOS. And during those seven years I sent plenty of money to places that many would call questionable.
If I count BOS as a loss, I still have only lost less than 1% of my bankroll. But when you factor in all the benefits of playing offshore (reduced VIG, line shopping, proposition wagers...etc) the risk of sending far outweighs the beneifts. Had a been playing with a bookie all these years, I'd have paid him far more in juice that I have lost being stiffed. So if you are going to seriously gamble, I think it's still a no-brainer in the long run to take advantage of the benefits the offshore world provides.