Taking sports bets on a server located in the U.S.
Taking sports bets on a U.S. server is the most clearly illegal activity, and as a result, probably no one has ever risked trying it.
Taking sports bets over U.S. phone lines. BetOnSports (2006, prison); Bodog (2012, pending)
Taking sports bets on a foreign server.
World Sports Exchange (2000; prison)
(details on above cases)
Facilitating the transfer of funds to online casinos (payment processors), and then visiting the U.S.
Processors serving FullTilt, PokerStars, Absolute Poker, & UltimateBet (2011)
Douglas Rennick of Canada (2010)
Ahmad Khawaja and Allied Wallet (2009)
(details on above cases)
Accepting advertising for Internet gambling, in the major media Google, Yahoo, Microsoft, The Sporting News (2003)
Esquire (2005) (more on these cases)
Helping people make bets on a website
Taking casino/poker bets on a foreign server
In December 2011, after they prosecuted the poker online cases below, the feds finally agreed that poker bets aren’t covered by the Wire Act.
FullTilt Poker, PokerStars, Absolute Poker (2011)
Party Gaming (2008)
Accepting advertising for Internet gambling, smaller media
IntegrityCasinoGuide.com (2006) (state of WA shut it down, not the feds; more)
Buying advertising in a U.S. publication as a casino, poker room, or affiliate
No legal troubles that we know of for this activity.
Placing bets yourself on the Internet
No trouble with the feds that we know of. A handful of states have anti-online-gambling raws, but even there prosecution is rare. (See the intro to this article.)
Taking bets on a server located in the U.S. (Risk Level: 5)
Taking bets (i.e., operating a Indian Matka casino, sportsbook, or racebook) on a website located in the U.S. is assumed to be illegal, and nobody does this in the U.S. for that reason. All Internet gaming websites are located in other countries where it’s legal for them to operate. (The U.S. government maintains that it’s not legal for them to serve U.S. players.)
Taking sports bets over U.S. phone lines. (Risk Level: 5)
Taking sporting bets over the phone lines is clearly illegal thanks to the Wire Act.
BetOnSports took bets over the phone, and were blatant about it, buying big billboards in the U.S. advertising their phone number. They were also really big potatoes, taking in $4.6 billion wagers from 2001 to 2005. In July 2006, their then-CEO, David Carruthers, was arrested while changing planes in Texas on the way to Costa Rica from the U.K. In April 2009 he pleaded guilty to federal racketeering charges, and in January 2010 was sentenced to 33 months in prison. The company’s founder, Gary Kaplan, was arrested in the Puerto Rico in March 2007 and in November 2009 was sentenced to four years in prison and ordered to forfeit $44 million in revenue. (He was reportedly released in Oct. 2011, according to Gambling911.) Kaplan’s brother and sister pleaded guilty in June 2009 to two felony conspiracy charges and agreed to turn over more than $6 million held in Swiss bank accounts. They were also sentenced to 10 months of house arrest. In December 2009, the company itself was fined $28.2 million. (GPWA, USA Today, The Register)