"Consideration" is a necessary element in any contract, oral or written.  So if the prospective payee says back to the prospective lottery winner, "If you give me half, I'll suck your dick once a day for a month," consideration would be satisfied.  An exchange of one promise for another is consideration.

The real problem enforcing oral contracts is what's called the "Statute of Frauds".  They are a little different in each state, but one of the common provisions is that an oral contract for payment of over X amount (used to be over $500, but law school was a long time ago), was unenforceable.  The reason being that oral contracts and their provisions are rife with potential fraudulent claims.  But one of the exceptions is that if the promissee does something substantial to his detriment in reasonable reliance on the promise, it might be enforced as a contract even if the sum is substantial.  Say for example, if the lottery ticket buyer let people at the party write down the numbers and days later when the numbers win, people at the party proceed to build a house or spend some money they otherwise couldn't afford, there might be a cause of action.  The catchphrase is "detrimental reliance".

A cute little movie was made in 1994 with Nicolas Cage, Bridget Fonda and I think Rosie Perez called "It Could Happen to You."  Cage plays a cop who makes a joking promise to a waitress (Fonda) to split his lottery ticket winnings in lieu of a tip.  Of course, he wins big and the story is how it affects the three main characters' lives.  Worth a look if you can find it.

-- Modified on 2/6/2014 1:40:42 PM