The likely problem with Sportingbet is that is takes bets from people living in a country (in this case the U.S.) where this is forbidden by law. Not all the authorities around the world act against operators that offer illegal services in their country, but the U.S. authorities clearly seem to be more alert.

In a reaction to the news, the online gambling shares traded on the London stock exchange plummeted. According to Bloomberg, shares of PartyGaming Plc, the world's biggest Web poker company, slid as much as 19 percent, to toda, while stock in 888 Holdings Plc, the largest online casino operator, slid 15 percent.

It is the second time in less than two months that a manager of a U.K. Internet sports- betting company has been held. Only two months ago, the CEO of online bookmaker Betonsports was arrested.