AdSense is easy. It takes minutes to create a text link and then you can blow out as much advertising as your bank account can take. That's scaleable.
Banners are a little harder. Someone has to draw it. It might take an hour or two, but once its done, you can repurpose.
When you do something a little more creative, it's harder. Things you can only use once don't scale as well, but they can be a lot more entertaining. Plus, its much more appealing to the consumer.
Rich media is a great example. When TV commercials get reporposed for internet video, its mindlessly easy to setup. However, the level of ease is only matched by the level of hatred people have for TV commercials following them onto the web. Easy to setup, easy to fail, to alienate... easy to never click a video again. When I hear the talk about YouTube monetization, I'm hoping we'll see some really creative advertising appear within this unique community, but I also recognize that it might be difficult to make happen.
Or, on the other hand, aren't brands looking for unique? Don't they want different? Certainly the agencies should be pushing this, no? For them to come up with unique applications for all of these web communities, it would be more revenue and more work... but hopefully better results as well.
So how do you create a tradeoff? Are creative campaigns destined to become more niche and more specialized, making them more appealing, but also less profitable and more people-heavy. Are there even enough talented creative types around to think of these creative brand interactions? How does creative and unique scale?