Alan is not a photographer. He is not a journalist. He is a web-developer that finds interesting photos across the news wire, and posts them in an appealing way. He has been posting at a rapid-fire, almost-daily pace fueled by a backlog of ideas, but expects things will slow down.
Alan explains on his about section that his blog is,
"Inspired by publications like Life Magazine (of old), National Geographic, and online experiences like MSNBC.com's Picture Stories galleries and Brian Storm's MediaStorm... The Big Picture is intended to highlight high-quality, amazing imagery — with a focus on current events, lesser-known stories and, well, just about anything that comes across the wire that looks really interesting."
(From Waxy, Kottke twice)