Matilda Reich asked why, in a world where everyone knows about the dangers of spam, and every email program has a spam filter, these dreadful messages just keep coming.

To put it bluntly, some people don’t get it. As George Carlin put it, “Think of how stupid the average person is, and realize half of them are stupider than that.”

Spammers don’t even need to count on the less intelligent half of humanity. All they need to turn a profit is a very tiny fraction of the population.

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Now then, about spam filters: They’re not perfect. Some spam will slip through. That’s not an accident; spammers work hard at outsmarting the filters. And once they outsmart a filter, they get a chance to outsmart a sucker.

Remember that a sucker doesn’t have to lack intelligence. They could be uninformed or fooled in a new way that few people know about yet. Or they could just be really tired.

It doesn’t take many suckers to make spam profitable. I’ve read estimates claiming that for every million spam messages sent out (including the majority stopped by filters), only three people fall into the spammer’s trap.

That sounds like a very bad business model, but it’s actually a very lucrative one. There are tens of billions of spam messages sent each day—possibly an many as 100 billion. That means 300,000 suckers a day.

Let me put it this way: If all I cared about was making money, and I didn’t mind breaking the law or hurting innocent people, I’d become a spammer. It’s a lot more profitable, and a lot safer, than breaking into homes.

Since spam is unlikely to stop, you need to remain vigilant. Don’t trust promises of cheap drugs, obscene pictures, or get-rich-quick schemes. If something seems too good to be true, it’s probably too good to be true. If a friend sends you a desperate message that doesn’t sound as if your friend wrote it, they didn’t.