Back when I started uploading to 23, I thought I'd never ever reach 1k. I was a Fl**kr pro member for almost four years and only got to about 400 photos.
Now I have 25 times that amount and still a serious number left in the pipeline.
I think the single most influential factor was Rolf from mtg, although I'm still not exactly sure why. It's not only about his photos, but also the vast number of topics and issues he mentioned that inspired me to go out and shoot more intensely and better prepared.