Get Tweets and Facebook Likes in Exchange for Free Content
I received an email from a wpliving reader asking how I went about getting tweets and Facebook likes in return for content on what has become the most popular post on wpliving: 65+ Free Seamless and Tileable Wood Backgrounds for Bloggers and Web Designers. Here is the original question:
I really like the idea of giving away some downloadable content in exchange for a like or tweet or other social site share. Can you explain how you accomplished that?
In this post, I’ll walk you through the process of setting that up. To get started, here’s a quick snapshot of the end result:

There are several ways of going about this, but it’s almost certainly going to require a WordPress plugin of some kind. The plugin I opted for is called Viral Lock – Like, Google+1 or Tweet to Unlock. It’s a premium plugin available for download on CodeCanyon.
Once you install the plugin, you get a little blue lock icon on your WordPress composition screen. All you have to do then is upload your content, retrieve the direct url to download the content from your server and paste the url in your WordPress blog post. Highlight the url in the post and click the blue lock icon to wrap it with a short code snippet. Publish the post and you’re good to go.
The plugin comes with a number of options including the ability to select different social media services that visitors can click to unlock the content. The main ones are Twitter, Facebook and Google+.
This is a simple but very effective way of generating some social media buzz around a specific post on your site and an interesting alternative to paying for content with cold hard cash.

If you are not willing to pay $16 for the plugin, maybe you try the free alternative in the WordPress Plugin directory: http://wordpress.org/extend/plugins/wplike2get
Thanks for your insights. Never heard about this plugin before, looks like a great plugin.