You receive a postcard or letter in your mailbox..gif)
You have won:
You know the answer is 5.
Some are advance fee scams. No legitimate sweepstakes makes you pay processing or administrative fees or taxes before you ever receive any money.
Others are timeshare sales hooks. Some promise cheap vacations that end up pretty pricey for second-rate lodgings. The majority are a high-pressure pitch for something you probably don't want or need.
Watch out for:
Mysterious mail offers promising the moon are more likely moldy, stinky cheese.