Poll: Who's Having the Worst Month?

It's been a May to forget for a growing number of the financial world's best-known names, including JPMorgan Chase's Jamie Dimon, Nasdaq OMX's Bob Greifeld, Chesapeake Energy's Aubrey McClendon, JC Penney's Ron Johnson, and Yahoo's Scott Thompson. We want to know who you think has had the worst month? Answer our poll and leave some comments.