A parable that may help you understand why developers of Twitter-related apps and services are so angry at Twitter after it changed its rules for them:

In 2006, a small restaurant called Twitter opened for business.

This wasn’t your typical restaurant. Twitter didn’t have its own chefs creating food. Instead, it invited anyone from the public to come into its kitchens and freely use the stove, pots, pans, plates and knives. There, they could make little scrumptious bites for anyone to consume.

Soon, word spread, and Twitter was bustling with people making their own food. Others, hearing about the wonderful bite-size snacks being made at Twitter, came in to consume them.

Twitter grew so quickly that it started to have major problems dealing with all the customers. Twitter’s lights would often go out. Plates and silverware were often dirty. There was never enough room for people to sit. Sometimes, unable to handle all the customers, Twitter would just be closed for hours at a time.

So Twitter came up with a plan: it told people that they could take the food being made in Twitter’s kitchen and give it away by creating new places for people to eat. Twitter called this the application programming interface, or A.P.I.

Soon there were food trucks, delivery services, meal messengers, all taking what was coming out of Twitter with its A.P.I. and redistributing it to people all around the world. Some of these distributors gave away Twitter’s stuff free. Others who had hired much prettier and reliable waitresses and delivery boys than Twitter started charging. As things grew, some decided to take hefty sums of money from investors to build specific businesses around Twitter.

Everyone seemed happy.

But Twitter soon realized that if it wanted to keep the lights on and pay those now very high gas bills, it would have to come up with a way to make money from everything being made in the restaurant. Around the same time, Twitter was placed under new management.

The new boss, Dick Costolo, realized that if the company wanted to make money, it would need to stop allowing all the food trucks and delivery services from taking everything made at Twitter.

So, Mr. Costolo decided that he would place advertisements next to the food people were making at Twitter. Twitter said it didn’t have much of a choice. It wasn’t a nonprofit. It couldn’t charge for the stuff coming out of Twitter, because it didn’t actually own it. It was being created by the public, after all.

This, understandably, incited the ire of everyone.

The trucks parked in the street were understandably upset. They had spent years building a reliable service to get Twitter’s wares to people. Now, they were at risk of being shut down. (Twitter had also, finally, set up its own army of wait staff, delivery people and food trucks and started giving everything away with ads next to them.)

The people who had come to Twitter in the early days also felt duped, as if they had been told their bite-size snacks were being used to feed everyone on the planet, not to make money.

So who was at fault in this tale? Really, everyone. The early Twitter customers and chefs should have realized that eventually Twitter would have to make money. That possibility included advertising. The food trucks that had set up shop on the corner, were in some sense, too idealistic, believing they could always get the food coming out of Twitter free. But most of all Twitter, which changed its decisions and strategy midstream, confused almost everyone, often hurting those who helped make Twitter successful and popular.

Twitter has always been a company that did things differently. It listened to the people who helped make all those wonderful bite-size snacks and it tried to adapt the kitchens, pots, pans and delivery trucks to make those people happier. But it is also driving out the food trucks that most directly compete with its restaurant operations. It may, in the end, make the people who eat the tasty bits happier.

The risk is that the fare starts getting really boring without the little flourishes the other servers delivered.

This post has been revised to reflect the following correction:

Correction: August 25, 2012

Noting that the definition of an A.P.I. is an application programming interface.