The is an undocumented character limit on the machine name for quicktabs blocks

I don't know what the exact number is but if one enters a machine name for a quicktab that is over a certain length then the block does not appear on admin/build/block and can't be used via a block reference in node content; which is one of THE SWEETEST use cases for quicktabs. . . getting tabbed views displays embedded in node content without breaking things (e.g. the javascript for views accordion) is not nearly as straightforward as you might expect / like.