All: We appreciate the votes and comments on this idea. As @bgeorge-eng
has noted, "Undo" is available in Analysis Workspace. Hopefully you have
all had a chance to get your feet wet with Workspace. We believe
strongly that it is the future of analysis on the web, and will be
investing heavily in adding more functionality there. Consequently, we
won't be adding Undo in Reports & Analytics or Ad Hoc Analysis.