I just picked up a copy of Photography Monthly for the bargain price of $10.25 U.S., and reading through to a blurb on pro photog Jane Mingay, she uses the photo site Clikpic, which *requires* that images have a maximum width of 600 pixels, or 600 high in portrait mode. Now, how serious can anyone be if they're showing landscapes at 600 total pixels wide? Is that what people mean when they say "postage stamp art?" At 600 pixels wide, you might see a tree trunk here and there, but no leaves as such. If I absolutely had to post on a site like that, I'd prefer to *crop* out portions of a landscape, with instructions for re-pasting, than just shrink the whole thing.
I wouldn't post on a site like that under any circumstances. Here's another one: Audubon magazine has a bird photo contest going: http://audubonmagazinephotoawards.org/
. Top prize is a trip to Peru. The catch is that in essence you turn over the copyrights to your pictures to them in perpetuity. I have a bunch of bird pictures like this one that are better than anything I've ever seen in their magazines or books but the idea that I'd just give away my copyrights is insane.