My suspěcion is that the stock business isn't going to be what it used to be.
Fragmentation of agencies isn't a good thing: it creates too many outlets that will probably never get visited. I can't seriously believe that any guy in an ad agency, looking to buy some images, will travel through a zillion little sites when he already has contacts with the majors. (Yes, I'm sure that exceptions can be rolled out, they always can.)
If there is a problem, it is with the big agencies becoming greedy and cutting the photographers' percentages down too far. I don't buy that it is increased overheads that drove this: wasn't digital business management supposed to simplify and reduce costs?
As for the micros, well, they oviously have their place for the amateur shooter who might not have made it into a major agency, but had the majors not betrayed their good suppliers...
Personally, I think the game is pretty much over. But I may just have been out of touch too long.