most people have facebook and do photo uploads
Facebook has "more than 400 million" active users. That's about 5% of the human population, or if we pretend like only North America and Europe exists, that's about 40%.
If we ignore Europe too, it's an amazing 120% of the population of North America.
The percentage of the people who use facebook AND upload photos is by necessity lower.
So, no, most people don't have facebook and upload photos, but most of your friends and family might.
Still: "More than 3 billion photos uploaded to the site each month".