For a long time now, we've heard that the reason we see so much spam in our email inboxes is because it works. Now, thanks to a security flaw on a spammer's website, we can see just how well it works.

According to an article in Wired News, an order log accessed at Amazing Internet Products showed that 6,000 people responded to an email with the subject line, "Make your penis HUGE." Considering most ordered two bottles of pills at $50 per bottle, you can see the company easily recorded over half a million dollars in sales during that period.

Wired said the customer list included the manager of a $6 billion mutual fund in New York, the president of an airplane parts distributor in California, and an elementary school lacrosse coach in Pennsylvania. All who ordered the product gave up their credit card information even though there was no way to contact the company: no phone number, mailing address, or email address.

Of course, there's also the little matter that penis enlargement pills don't work. When Wired asked one man why he responded, he said, "There was a picture on the top of the page that said, 'As Seen on TV,' and I guess that made me think it was legit."

As long as there are people like that in the world, no amount of anti-spam effort by AOL (NYSE:AOL), Microsoft (NASDAQ:MSFT), or EarthLink (NASDAQ:ELNK) is going to help. Barring some drastic legislation by Congress, we're all doomed to continue receiving ads about farm girls, free cable, Nigerian businessmen, and, ironically, spam-blocking software.

What does it all mean from an investing perspective? Bill Mann has that answer.