Good to see you on WebmasterWorld, I've seen you posting a lot over at a4u.
It's a couple of interesting questions you ask. Firstly with regards to CPM deals working, they can be very lucrative on the right site with the right campaigns. Having said that I don't think there are many decent campaigns (high CPM rates, targetted to the site) coming from the run-of-the-mill ad networks like fastclick, valueclick, advertising.com etc. All the good campaigns we've had for the last few years have come from small niche ad agencies, often liasing directly with large clients media divisions. Unless you have a large traffic volume, in a pretty small niche you're going to struggle to get these kind of campaigns. What we tend to do is keep certain ad spaces open, run the decent campaings as and when they come and then backfill with run of network cpm when we aren't running anything targetted. The difference in revenue between these 2 types of campaigns is often an order of magnitute. Unfortunately the 1999-2000 days of £20-£30 cpm are gone :(
The only campaigns we've run in the last year approaching that kind of level are rich media overlays, which can work great if they are well thought out, extremely targetted and capped.
I think your other question is why don't more webmasters run CPA/affilate campaign in addition to CPM/CPC and I think a lot of this has to do with expectations and experience.
Take the following scenario:
A relatively inexperienced webmaster has a couple of sites running cpc/cpm banners from a network such as fastclick. They don't make a fortune but it pays a bit, they're also running adsense which is easy for them to implement. They come on WebmasterWorld and start reading about affilate marketing. 'Great' they think, they sign up, grab some code and replace their fastclick banners with an affiliate programme. Then they sit back and a couple of weeks later realise they've only had a handful of clicks and no sales. They get dejected and reject affiliate marketing as not working for them, or being too hard.
I think a large chunk of the reasons many webmasters don't run CPA is because they think it'll work just by slinging a couple of banners up - which from your job, I'm sure you know isn't the way to go.
I've waffled on a bit I think, but fundamentally I think many new webmasters don't see affiliate marketing beyond putting up a few banners and waiting for the sales to start rolling in.
<edit - typos>