Reddit has a subreddit called Random Acts of Pizza that randomly gives out pizza to people who ask for it.
In /r/Random Acts of Pizza, users explain why they want pizza and other users choose whether or not to buy that individual a pizza. Since pizza can be ordered online and sent to someone’s house with just a few clicks, it’s easy to see why Random Acts of Pizza has such a popular following.
It’s so popular, in fact, that a professor recently developed an algorithm that explains the likelihood of somebody getting free pizza after posting on the subreddit.
Here’s how that professor developed the algorithm and studied the subreddit:
-The professor, Tim Althoff at Stanford University, downloaded and analyzed the entire history of the subreddit – including 21,000 posts in total
-Althoff then filtered out posts to identify posts where people successfully earned free pizza – a total of 379 posts
-Then, he analyzed those 379 posts to determine how they earned free pizza
-After analyzing the posts, Althoff developed an algorithm that predicted, with 70% certainty, whether or not an individual would successfully receive free pizza.

Which post qualities get free pizza?
How do people earn free pizza online? Here are some of the qualities that make your free pizza request more successful, according to Althoff’s algorithm:
-Narrative: Tell a story about your family, being poor, losing a job, moving to a new town, etc. to increase your likelihood of free pizza.
-Reciprocate: If you promise to return the favor in the near future, you’re much more likely to receive free pizza today.
-User history: People who arrive at the subreddit with no comment karma, link karma, or previous post history are unlikely to get free pizza. People who have a relatively high karma status and have regularly contributed to both Reddit and Random Acts of Pizza are more likely to receive free pizza.
-No pleases or thank you’s required: Although Reddit appreciates a post-pizza thank you, good manners didn’t indicate whether or not a post would be successful. You could be exceptionally polite or say no “please” at all and you’re equally as likely to get free pizza.

Of course, this professor probably ruined the subreddit forever. One of the main attractions of the subreddit was its tight-knit community of like-minded people who just wanted to help out a fellow human being.
With professors developing algorithms for gaming the system and more media attention coming to the subreddit, it’s going to be increasingly difficult to separate the trolls from the people who genuinely need a warm meal.
Still, Random Acts of Pizza is one of the few places on the internet that continues to do good deeds.