I hadn't looked at Geni in a while, but when I first used it, it was an awesome site to build your family tree - if you care about such things. It recently notified me that there are other family trees out there with my relatives on it, but they now charge monthly for me to find out more. Other features they added were statistics on your family - average life expectancy (59 male, 63 female for my family), age and birth month distribution. Handy, but a bit compulsive if you ask me.
Regardless, they are popular enough that people have entered some famous people, presumably distant relatives, or in a wiki-like manner in the pursuit of complete knowledge they have entered the well know family trees of well known people. Shakespeare and Dickens are here. Is Jesus and his Mom and Dad here?
And check out the link to contact Shakespeare's manger. I wonder who gets that email?