This issue was raised and closed last year, but I am still finding it happening. If you specify a height of less than 424px, the bottom of the likebox is truncated so that you cannot see the bottom border. If it's much less than 400px, you cannot see the bottom arrow of the scrollbar either. Either way, it gives a less than ideal user experience.
You can reproduce it easily on the code generator page: http://developers.facebook.com/docs/reference/plugins/like-box/ by specifying a height of less than 424px and generating the code. Then close the code box and look at the demo.
I would post images of this, but I don't have enough reputation points, so you'll just have to try it for yourself.
This happens on IE8, FF and Chrome. The exact height varies, but it truncates on all three given insufficient height.
