Failed get-rich-quick scheme - automated video poker
In the early days of web casinos, "Intercasino" was offering play-over-the-web-with-real-money games, including some full pay video poker games that, as far as I could determine, were positive expectation with perfect play. (Casinos sometimes offer VP games with a small positive return because ideal strategy is unintuitive and most people make more than enough mistakes to give up their edge.)
I liked the idea of being able to sit at home clicking buttons with the mouse and earn Big Money other than the fact that it was really really boring. I liked even better the idea of having my computer sit at home clicking buttons to earn Big Money while I sleep, work, travel... If it worked, I ramp up to bigger bets, then roll the profits into buying more computers to do the same thing until the casino finally caught on and changed the games.
So I wrote a program to play video poker over the web. My program looked at the screen, recognized the card values, decided which cards to discard, and clicked on the screen to play the game. At first I put it in an "apprentice" mode where it made the decisions and clicked the hold buttons but I had to hit OK before letting it draw. Occasionally it made boneheaded plays based on poor recognition (for instance, confusing the Queen of Clubs with the Queen of Spades) but I kept fixing bugs and watched it long enough that eventually every time I stopped it and said "wait a minute - is that the right play?" it turned out that I was wrong and the program's play was correct. So, I let it run on its own.
The casino had an offline practice mode where you weren't using real money. When my program played in practice mode, it won at roughly the rate I expected. But when it played in real mode, it lost. It's possible I was just being unlucky, but I think the casino was cheating; they rigged it so the big, rare bets don't pay off as often as they are supposed to. After losing a few hundred dollars (a speculative investment from my personal blackjack bankroll) I decided I didn't have enough confidence that it was an honest game and pulled the plug on the experiment.