Early Access can be a boon to developers and gamers, but it has risks. You are, after all, paying for a game that's not finished and may never be—or that may not turn out to be exactly what was promised when it's done. Valve took steps earlier this year to clarify the realities of Early Access games for consumers, and now it's updated its rules and guidelines for developers as well.
Giant Bomb reports that Valve recently distributed updated Early Access policies to developers, broken down into separate rules, which must be followed, and guidelines, which should be. The rules are fairly straightforward: Developers must specifically label their games as "Early Access" when distributing Steam keys off-site (through a Humble Bundle, for instance), and are no longer supposed to make "specific promises about future events," like when a game will launch or a particular feature will be added. Finally, Early Access launches must take place at the same time as releases on other digital storefronts, and developers cannot charge more for their Early Access releases on Steam than they're charging elsewhere.
While the rules are designed to protect consumers, the 'guidelines' seem aimed more at keeping overly-optimistic developers from getting themselves into trouble. They recommend that developers don't launch in Early Access if they can't afford to continue developing the game with few or no sales, and that studios "set expectations properly" when talking about their projects. Developers shouldn't launch into Early Access without a playable game—"If you have a tech demo, but not much gameplay yet, then it's probably too early to launch in Early Access"—and on the other end of the scale, games that are effectively finished are also not appropriate for Early Access.
Even with these new rules and guidelines in place, there's still (and always will be) an element of risk to Early Access games. Some will be success stories, others will be smash-and-grab disasters, and a lot of them may just run out of gas and fade into a limbo.