Isn't it something like http://www.paywithatweet.com http://www.paywithatweet.com but also includes FB, Google+ and linkedin? For those who are concerned about

Isn't it something like http://www.paywithatweet.com http://www.paywithatweet.com but also includes FB, Google+ and linkedin? For those who are concerned about seeing the content first before sharing it, it can be a nice idea to use it with a free online version. E.g., few days back I downloaded pdf version of "Noobs guide to online marketing" (http://www.seomoz.org/blog/the-noob-guide-to-online-marketing-with-giant-infographic-11928)and http://www.seomoz.org/blog/the-noob-guide-to-online-marketin... it asked me to pay with a tweet about the ebook.