The immediate first example I thought of was the original TJW with the Joker's Jackpot. Originally, you had to win 5 games in a row to claim the Jackpot, but it was later shortened to 3.
Another: On syndicated $ale, reducing the lot win from $830 to $750.
And still another: GSN's Chain Reaction (Season 1) making the target numbers of correct answers to double and triple your team's winnings from 7 and 10 to 5 and 7, respectively.
One more for four (that rhymes!): On Million Dollar Password, if a player made it to the $250,000 level, he/she could go for the million with no risk in Season 2, while he/she had to risk that money (well, all but $25,000) to do so in Season 1.
Anthony
P.S. Thanks for the brief distraction from grading final papers!