Guys, I think you are reading all these changes wrong. They are not just business decisions, but - my diagnosis - business decisions dictated by IT side (sure, nobody will ever admit this)
Translation from a professional point of view (not stock photo, where I am brand new)
"Sorry, guys. We just had hit our scalability limit. We thought we were linear, but it appeared that we are exponential (sorry for a lingo). We _cannot_ afford any more photos, especially taking in account our new contracts. Our site will just fail.
The main bottleneck is our search, so the only way to S-O-A-s (other than to stop the growth) is to limit the multiplication factor - keywords. But, to be safe, we'd better do both.
We've developed an excellent software, and the fact that it does not scale is an act of God. All other sites are probably using some infernal knowledge. Hiring new specialists will not help, as we are the best of the crop, and, BTW, costs $$$$".
This is not a pure speculation, key points were verified by looking at the site behavior from the same professional point of view.
Do not take me wrong, I
really like CanStockPhoto, it is a big pleasure to upload there (though not a pleasure to get close to $0 back), but...
Uncle Gene,
digging his own CanStockPhoto future grave
P.S. to Duncan:
http://www.amazon.com/gp/reader/0672326140 - very useful, especially if read open-minded