When logging in on an iPhone or iPad, the username textbox auto capitalizes the entry. As the field is case-sensitive, I was wondering if you could try to disable this. I realize you don't spend much time offering support for mobile devices on HN, but this could prevent a lot of bad logins from occurring.I'm not 100% if this would work, but you may be able to add an "autocapitalize" property to the field in the form. See: http://dotnetperls.com/iphone
Any web designer should be able to confirm if this could work.