We built WP Responsive FB iframes for 2 reasons.
Reason #1. On all of our client sites we use the Facebook page plugin to create the facebook fan page gadget.
The issue is that the iframe embed is not responsive. We use it mostly in WordPress Widgets. The issue is that when creating the widget we want to set it at 480px wide so that it shows good in larger mobile phone. If set it at that – most sidebars are smaller than that – so we end up with this
If we reduce the width of the widget to 320px this is what we would see
So we built a plugin WP Responsive FB iframes that you just install and activate and it resolves the issue. There are no settings it just adds the code code to your site.
Here is a test with the facebook like box in the viewport