I just noticed today that the data-width attribute for the Facebook Like Box widget does not appear to be working. It looks like it is reverting to the default width. An example
According to Facebook official like box page, The minimum width is 292px.
Still, there is a little project on github to make facebook like box responsive and adapt to your website layout.
Applying this along with setting the width of the container to any width you prefer will force the facebook like box to fill that container and adapt to its width, no more, no less:
/* This element holds injected scripts inside iframes that in some cases may stretch layouts. So, we're just hiding it. */
#fb-root {
display: none;
}
/* To fill the container and nothing else */
.fb_iframe_widget, .fb_iframe_widget span, .fb_iframe_widget span iframe[style] {
width: 100% !important;
}