This was somewhere around 1999 or 2000. I was still running Windows 95 and was completely in awe of this new and exciting place called the Internet. IP telephony existed, but the voice quality was so poor that almost all voice calls still happened over landlines.
Thanks to the Wayback Machine, I can see the page as it existed in 1999.
Around that time I came across a website called Keen.com. Yes, the same Keen.com that today is all about psychic readings and other kinds of mumbo jumbo. Back then, however, they had something that was genuinely brilliant for that time: an online marketplace that brought together “people with problems” and “problem solvers”.
If you had a problem, you could browse a directory, find someone who knew the answer, a computer guy, a gardening expert, or an accountant for example, and speak to them over the phone for a flat per-minute fee.
The clever part was that there were no international call charges.
Instead, the customer would dial a local toll-free number and hang up after the first ring. Keen’s system would immediately call them back, connect them to the expert, and charge only for the conversation. At the time, calling from Dubai to the United States would cost significantly more than making the same call from the United States to Dubai, and Keen cleverly took advantage of that price difference. A few years later, callback services and international calling cards also used the same trick.
Now Keen rewarded every new user with a $5 welcome bonus. If someone referred you, they received another $5.
Being a curious teenager, the first question that came to my mind was:
“How do they know I’m really a new person?”
The answer was simple.
Your landline number.
Back then, email addresses were free to create by the dozen, but landline numbers were scarce. Keen assumed that one landline meant one person.
A perfectly reasonable assumption.
Except for one small detail: a telephone number can sometimes be represented in more than one way and still ring exactly the same phone. The telephone exchange understands they all refer to the same destination. Keen’s registration system didn’t.
One evening I registered another account using exactly the same landline number, but with two extra trailing digits. It worked, and I was five dollars richer.
So I tried again. It worked again. Then again.
The same telephone kept ringing in exactly the same place, but Keen happily believed it was a new account and handed out a $5 welcome bonus.
As a teenager, I was amazed that something so clever could overlook something so simple.
That was my first lesson in computers: computers are only as good as the programs they run.
The assumptions programmers make may seem perfectly reasonable, until someone comes along with a real-world example that proves them wrong.