It's a common mistake to attribute the success of Facebook to its features (it boils down to microblogging + threaded discussions). The usefulness (i.e. product from a marketing perspective) of Facebook isn't its features, it's the people who joined it. Look at Google+, it's not that bad in terms of features. But it lacks people, therefore it's not a competing product. A competitor would be not someone who does 50% of what FB does. It would be someone who has 50% of what Facebook has.