One of the first things we noticed about Android's new vertical, gesture-based multitasking UI was that the option to clear all recent apps from the list was nowhere to be found. According to VP of engineering for Android Dave Burke, though, the change is temporary.
At the Android fireside chat at Google I/O, an audience member asked Burke why the button had been removed in the first place—a question met with applause from many in the crowd. Burke said he had the same question, and (somewhat smugly) deferred to a member of the Android team in the audience to answer.
"Android is managing the memory as well as you can," the team member explained. "You don't need to be swiping things away for Android to be able to reclaim that memory in order to be able to run other things." He then apologized and said the team is "looking at bringing it back."
It's true that dismissing recent apps en masse doesn't really do anything for your phone's performance, but clearly, people like being able to do so.