I think that the whole Facebook dust up around privacy really has brought us a new pick any two triangle diagram:
The New Pick Any Two
When it comes to some kind of online services you only get to pick two of: privacy, no effort, and no cost. With free services, that you don't have to manage yourself, it should be no surprise that you have to give up privacy.
I'm sure there is a better wording for the pyramid, or even a better distillation of the legs. If you've got any thoughts on that front, please post a comment.