Dry Ice Factory

How I'd put it is that Facebook is close to being a pure example of ping. Anything which allows for response is a ping device but in the case of LiveJournal (or any number of other networks where original work can be posted, Flickr, deviantART etc, etc) there is also the satisfaction of creation. As you yourself have noted writing reviews to post here fills a need other than connecting with others. If you write a review and nobody responds you still have the satisfaction of creation because writing that review has allowed you to examine your response and set it out in a coherent way. Facebook on the other hand isn't really about creation (though you can use it that way if you try hard enough) but about taking quizzes or posting videos etc, activities which require little or no creativity, and sending the results as a ping. In the Facebook model then the ping is the most important part of the process, so long as other people keep sending you quizzes and videos you know you're in the social loop.