While I can certainly understand why professional photographers are afraid of micro-payment, I think George Munday (along with others) is making a flawed assumption that's lies at the root of the fear.
The fear is that the price will drop by 100x, but the volume of sales will stay the same, resulting in a 100x drop in revenue. George himself states this when he says "Since then it has sold 42 times making approximately $10.000 of which about 40% came to me. If it had been sold through a Micro Payment Agency it would probably have made a shade under $100.00"
How many people owned digital cameras when they cost $10k each? How many own a digital camera now that you can get them for $100? Think it's the same number of people? No, the market generates orders of magnitude more revenue than it did when cameras were $10k "professional tools". They reached a price point where, not just the dedicated professional, but even "the common man" could afford to buy one -- even if they didn't really need it in the first place.
I believe the same will happen with stock photos, thanks to the micro-payment agencies. Let me give you my example: I'm not with an advertising agency. I'm not a designer. I don't make my living selecting photographs for magazine spreads. But, as part of my job I do a lot of PowerPoint presentations. I like to illustrate these with photos instead of the ugly overused clip art that's available, and spending $10 to $20 doesn't bother me. Would I do the same if a single photo cost me $1000 (or even $100)? Absolutely not. Would I do it if I had to negotiate rights to use a photo, and guess at what I was going to do with the PowerPoint in future? Absolutely not.
Micro payment sites have made photos accessible to me, the "common man", not a "professional". Are there others like me? Yes, and there will be more and more as the market matures -- orders of magnitude more than the buyers in design houses and national magazines.
But, step back and ask yourself, "today, without micro-payment sites, what would someone like this yahoo do?" They'd do what any god fearing American would do: they'd do a google image search and steal, for their own use, the image they find. But, they'd turn a blind eye to it, because there was no accessible, reasonable option.
Would easily accessible and easy to use micro-payment sites change this? Ever heard of something called iTunes? Before iTunes, people copied (illegally) most digital music, because it was the only way to gain access to the content. iTunes changed all that by providing an accessible and reasonable option -- because people like to do the right thing... if it's easy. It's increased overall industry revenue, not decreased it.
Will the much larger market created by micro-payment sites change the types of photographs people buy? Probably. And, that will be a windfall for some photographers and a terminal blow for others.
If I were in the shoes of a professional photographer, I wouldn't fear micro-payment sites. I'd fear that they aren't easy enough to use, easy enough to find, easy enough to subscribe to, easy enough to search; I'd fear they didn't have gift certificates and other simple/novel forms of payment. I'd fear everything which could marginalize their ability to grow the overall market.
What else would I do? I'd be yelling at Google to buy/team-up with a micro-payment agency and integrate it into google image search ("If you liked this copyrighted image, here's 15 similar ones you can legally use for only $5"). And, if I really had my way, I'd give the micro-payment stock photo site an extra 50% of my potential revenue if they shared with me the frequency of all the search terms used on their site, so I could optimize the types of photos I produced to maximize my revenue.
In the end, change is hard. Change is fearsome. But, if you're open, thoughtful, and adaptable, change can be very good. Oh, and one more thing I almost forgot: you can't stop change no matter how hard you try.