Steam Early Access was intended to be a way for developers to test their products and receive feedback from the players. But recently, many developers have been taking advantage of this service. This could mean releasing a game in a completely broken format just to take money from the consumers to never finish the game, or just never releasing the game once it's been put into Early Access.
According to Valve, Early Access is supposed to be a "place for games that are in a playable alpha or beta state, are worth the current value of the playable build, and the developer plans to continue to develop for release", and games should also be in a finished state upon Early Access release.
While this service has had some great games released because of it, such as Day Z, many games have also done many unfair things to the consumer. In May, Earth: Year 2066 was released as broken and unfit for sale. Valve has realized their mistakes with the Early Access service, and they have now updated their guidelines with four new rules developers with hopefully follow.