istock and shutterstock vs "pro stock" sites

This thread on dpchallenge says that, “istock / shutterstock are ruining the industry”.
SharQ recommends Alamy, Corbis and other sites that sell photos on a royalty basis. istock/shutterstock sell royalty free photos so photographers could be “underselling” their photos. It’s an interesting thread and worth a read.
According to their FAQ, Alamy require 48MB tiffs (24MB for “reportage material”) which my camera might have a little trouble creating. By upscaling a 2048×1920 photo to 3584×2688 the resulting uncompressed tiff file is 28MB. *ouch* It might be a while before I submit stuff to them!
Meanwhile, in the world of the amateur photographer I’ll continue to use the “royalty free” sites such as istockphoto and shutterstock.
Here’s a thread about how well some users of those sites are getting on. Note to self, upload more photos!