Valve has updated Steam's FAQ to warn customers that some Early Access games might never get finished.
Originally, the question "When will these games release?" had the answer "It's up to the developer to determine when they are ready to 'release'. Some developers have a concrete deadline in mind, while others will get a better sense as the development of the game progresses."
The answer has since been updated to make it clear that some games might never get finished. "You should be aware that some teams will be unable to 'finish' their game," the FAQ currently states. "So you should only buy an Early Access game if you are excited about playing it in its current state."
Evidently, a sizable portion of Steam customers misunderstood the platform's Early Access option as "early access" to finished-yet-still-unreleased games.