numerically, quite low, but given the number of people on the internet, it happens routinely. I'd guess most English speaking people have used <internet_search_of_choice> for their name and found duplicates So:
guess maybe 100 million English names on the internet, between 2 and 100 matches, so around 1 in 10 million
BTW. I got bored counting the matches for Jacob Bartlett on facebook. definitely more than 10
I've never met anyone (outside known relatives) with my spelling of surname. When I moved to my current UK city I was surprised to find a Firstname Lastname match in the same city.
Facebook shows dozens of the same name in the general area.
As I've seen some say, if you're one-in-a-million then there's ~7000 people like you out there somewhere!
Jacob and Bartlett are both relatively common names, I'd say aggregating over a lifetime one can expect to coincidentially bump into quite a few over the years (since the advent of the internet at least!)
guess maybe 100 million English names on the internet, between 2 and 100 matches, so around 1 in 10 million
BTW. I got bored counting the matches for Jacob Bartlett on facebook. definitely more than 10