John Piper, on the lottery craze, had some good words against buying tickets.
For the short version:
1. It expresses a sinful desire to get rich - 1 Tim 6:7-10
2. It is poor stewardship and embezzlement from God, who has entrusted you with your money. Good stewards go and work with what they are given (Matt 25:16).
3. The chance of winning is so small, it is basically throwing your money in the garbage.
4. The system is built on most people losing money.
5. It is a tax on the poor, who buy most of the tickets.
6. You could use the money better, elsewhere. Invest it, tithe it, give your wife a gift.
7. It undermines virtue, rather than encouraging it.
Or is it harmless entertainment? How is it different from playing a game at the fair that you'll probably lose? Doesn't it raise money for good causes?