I've seen a lot more iPhone 3G's than 2G. When I had the original iPhone I felt extra cool because very few people seemed to have one Now everywhere I go there are iPhone 3Gs. Apple stopped selling the 2G after the 3G was released so it's not like people are choosing to purchase 2G's instead of 3G's. I think you just happen to see a lot of the originals floating around. I seem them very rarely.
Yep, all US Apple Store employees got free iPhone 2Gs. A lot of Americans bought iPhone 2Gs as well, and may not have felt 3G was a needed upgrade.
Also, people who unlocked -- until recently -- had to stay with the 2G.
*Lot's* of iPhone 2Gs at Macworld this year.
I live in a rural area that doesn't yet offer 3G so I'm staying with my 2G and saving $10-/month. It does almost everything. I've got GPS in the car and even if I had a 3G most of the location based services would only find deer and turkeys! Seriously, though...we just don't have Starbucks on every corner so using the various social networking to find my friends via GPS just doesn't play here! I think that a lot of people are holding on to their 2G iPhones until there is a really compelling feature available that they can't get on the 2G.