http://glennreview.com/viral-payment-software-review/ VPS is the first of its kind micro payment/ cloud based content locker referral system.
The problem with current content lockers is that they are plugins that simply shade over the content to be locked but in fact if anyone goes into the source of the site you can access all the content you like.
VPS goes out of its way not only as a content locker but also integrates with paypal as a micro payment locker. Where a user must pay $1 or whatever said amount is to unlock the content/article/download page or coupon.
Not only this but VPS gets extremely exciting where it unlocks content based on a referral and leaderboard system. THIS is an extremely powerful viral system that will automatically get the user more traffic to whatever offer they have running.
What I mean by referral is that a customer landing on a website must refer a specific link however many times to unlock the said content/coupon/discount etc. When the referral number is met in VPS the page unlocks to reveal said content.
In regard to leaderboard, whoever shares the locked content the most and whoever builds up the most points will get the content unlocked.