With a single click WP Share To Unlock will lock content on any post/page, including videos, to get viral traffic from Facebook to your website.
One of the nice things about this plugin is that you don't have to do a lot of configuration, setting up FB apps etc. The short code to lock the content can be placed anywhere, around the whole post or just a part which is useful. (I wanted to lock down a video but leave the rest of the content as a teaser.)
Regarding functionality, I also initially saw the issue reported by the other reviewer with not refreshing on clicking like, but I checked out the rest of my plugins and found there was a conflict between two which happens sometimes. When the culprit was deactivated this plugin worked fine and immediately unlocked the content as expected.
I also noticed that the author has provided a direct link to enter a ticket at his support desk right inside the plugin settings screen, which is a little better than just hoping the dev swings by the forums.