The O'Haras and the Gattos appear to have no internet presence at all - they're the branches of my family who I haven't encountered in my research.
The Gillans I've met primarily on surname message boards, though one also landed here after a Google search.
The Mulcahys are extremely fond of Googling their grandparents' names. Several have found my blog by doing so.
The Mulvaneys, on the other hand, are prone to doing genealogy. I've connected with a number of them through Ancestry family trees, and we have a nice little group of people to share research with as we find it.
The Lanzillottos do genealogy, too, and I've encountered a couple of them through Ancestry.
(As I write this post, though, I think I might be creating some of these tendencies instead of just witnessing them. Have I visited message boards for all my surnames? And I realize that I have one or two posts where I list all the Mulcahys and their spouses - of course their grandkids can find them by Googling their names! I guess I need to get on that with the rest of my lines - too bad there's no big family picture like the one that was the catalyst for the Mulcahy posts.)