Prosecutors won't charge marijuana possession cases anymore, starting December 6th:

Ian Goodhew, deputy chief of staff for the King County Prosecuting Attorney, says his office is trying to figure out how if they will charge the marijuana possession cases are pending. "We haven't figured out how we will handle all of those cases," he says. But assuming the possession portion of the law is not federally challenged -- and no credible lawyer thinks the possession portion can be -- Goodhew says that in future cases, "we cannot charge someone under state statute."

...and police won't make possession arrests:

Sergeant Sean Whitcomb, a spokesman for the Seattle Police Department, says this: "For us, the law has changed, and people can expect no enforcement for possession."

Or to put it another way: Yesterday Really Happened.