Seeing threads and blogs asking about Members' Choice, I thought it's a good idea to collect our Admins rare replies to this frequent question - which is not found in FAQs by the way :P
Message posted at 11/22/2006, 16:09:40 PM by Achilles:
They are selected randomly from the photos that received most comments.
Message posted at 09/30/2007, 15:12:35 PM by Sebcz:
Yes, it is based on comments a photo has. When you use a photo as the means of talking to another members, it's picked up by the system.
So there you have it!
Here's my first ever members' choice, it's when I learned about this whole thing :)