The idea of paywalls is nothing new. Sites such as NYTimes.com have been using such an approach to get people to subscribe. People may not be ready to pay for your content. But you can always ask them to help your articles go viral on Facebook, Twitter, or Google+. These plugins help you do just that:
Twitter Content Locker: a pretty decent plugin to promote your content on Twitter with. It hides parts of your content and unveils them as soon as your visitors retweet your story.
Viral Lock: this plugin supports Google+, Facebook, and Twitter. It makes your content go viral by forcing your visitors to share your content before seeing the rest of your work.
Pay with a Like: gives your visitors multiple ways to pay for your content. It works for Twitter, Google+, Facebook, and LinkedIn.
Facebook Traffic Pop: this plugin does not restrict access to your content permanently. But it does require your visitors to wait a few seconds before being able to access your articles (unless they like your posts that is).
WordPress Like Locker: a Facebook like locker plugin that asks your visitors to “like” your article before they can see it.
Like Gate: a free plugin webmasters can take advantage of to increase the number of likes their articles get. Just use the appropriate tag to lock certain segments of your posts and this plugin does the rest.
Google +1 Content Locker: very similar to the first plugin but this one encourages your visitors to vote for your articles on Google+.
Have you tried any of these plugins? Which one are you impressed with the most?