How many people do you think you have met in your lifetime?

[muon2]

#1 is necessary, and one of the next two, to qualify:

1. Have communicated

2. Have seen in the flesh
3. Know their name


Going by that, I'd guess somewhere in the vicinity of 8-12,000.

Must it be two-way communication? For instance, giving a lecture in a university auditorium is communication for both the lecturer and listener and they see each other in the flesh. In this example, the listener would count one additional person, but the speaker would count the number in the hall.

[muon2]

After meeting dozens of new people almost every day for the last week, I'm pleased to say I met no one new except for the host and waiter at the restaurant and the ticket attendant at the the movies.

So on to the estimate. These days I estimate I meet about a 100 new people a week during the first half of the year and about half that number a week for the rest of the year. That's about 4000 a year at my current level of activity which has been the last six years. The six years before that I was probably at nearly that number and the decade before that half again as many. Between classmates, conferences and extra-curricular activities, 1000 people a year was probably about right for high school through graduate school. Prior to that the number would have been substantially less, but I moved frequently during my first 10 years so the number was probably above average. I'm guessing that I'm at about 100 K in round numbers.

[muon2]

As in actually spoken to? Probably ~500.

I highly doubt you've only spoken to ~500 people in your life, unless you live a very sheltered life.  I mean, think about how many people one must exchange only a few words with and never meet again, like the checkout person at some store you buy something at (though I guess that's becoming more automated these days).

Morden is right. It's not hard to meet three new people a day by the above definition. A key is that names not be known, just some form of communication between you. Just yesterday I only left home once to eat out and see a movie, yet that generated three new meets. Most retail purchases will involve a meet, and for me most are new.

At three a day, you get about 1000 a year. For PiT, it's a perfect example of a Fermi problem.