JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="//netdna.bootstrapcdn.com/twitter-bootstrap/2.2.2/css/bootstrap-combined.min.css">
<script src="//netdna.bootstrapcdn.com/twitter-bootstrap/2.2.2/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/underscore.js/1.4.3/underscore-min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/underscore.string/2.3.0/underscore.string.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/backbone.js/0.9.10/backbone-min.js"></script>
<div class="container">
<form class="">
    <div>This form is fine!</div>
    <div class="row">
      <div class="span8">Span 8</div>
      <div class="span4">Span 4</div>
    </div>
    <div class="row">
        <div class="span8">
            <div class="control-group">
                <label class="control-label">Nameddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd88888</label>
                <div class="controls">
                    <input type="text" class="span8" />
                </div>
            </div>
        </div>

        <div class="span4">
            <div class="control-group">
                <label class="control-label">Age</label>
                <div class="controls">
                    <input type="text" class="span4" />
                </div>
            </div>
        </div>
    </div>
</form>

<form class="form-horizontal">
    <div>This form is broken!</div>
    <div class="row">
      <div class="span8">Span 8</div>
      <div class="span4">Span 4</div>
    </div>
    <div class="row">
        <div class="span8">
            <div class="control-group">
                <label class="control-label">Name</label>
                <div class="controls">
                    <input type="text" class="span6" />
                </div>
            </div>
        </div>

        <div class="span4">
            <div class="control-group">
                <label class="control-label">Age</label>
                <div class="controls">
      ...

CSS

.form-horizontal .control-label {
    width: 100px;
}
.form-horizontal .controls{
margin-left: 120px;
}
@media (max-width: 480px) {
.form-horizontal .controls {
margin-left: 0;
}
}