twitter/bootstrap — pull request #8622 by jholl (2013-07-26 13:13:42+00:00)
Title: use .form-group in .form-horizontal for application of consistent vertical form spacing

Not totally sold myself on this but with .form-group having margin bottom, might be more consistent to use this in .form-horizontal instead of using .form-horizontal .row + .row. - here's jsfiddle but pretty clear http://jsfiddle.net/jholl/Qfv36/

Things I don't like:
* adds extra mark-up
* forces use of a margin at bottom of form or awkwardly drop class .form-group on final div...

Things I do like:
* all form vertical spacing can be controlled with .form-group
* feels more consistent application of .form-group for new users

@mdo, you decide.