Scratch off tickets are one of the dumbest "bets" out there...
An example from Nevada:
Scratch-Off Tickets
In instant scratch-off games, the state takes about 50% of the action. 34% going to public education and the rest covering administrative and promotional costs. The remaining 50% is returned in prizes. Since the state keeps 50 cents of every dollar bet, the house edge is 50%, making the scratch-off game worse than any game in Nevada.