According to the page, "There are 3,630 people in the U.S. with the last name <510>." If you're one of them, and you're descended from the English 510s rather than the Dutch 510s, you and I are related somehow. We might have to go back as far as 1630 when the first 510 arrived on these shores, but (according to the family association) there *will* be a link there somewhere.
Coming from a micro-family as I do (on my mother's side of the family, I am the only grandchild; on my father's side, I was the only grandchild until age 10, and grandkid #3 didn't arrive until I was 26) it was very, very strange to go to the family reunion and realize that I was somehow related to every one of the 75 people in the room.
spiritualmonkey, who has 21 first cousins, was completely unfazed.
[ETA: The figures on that site are verrrry suspect — it claims that there are 0 people with Pirate's family name in this country, and I can think of at least 10 off the top of my head.]