After seeing ad revenue plummet, I had a long discussion with some of the people at Google and they recommended the change. Apparently, the old text ads I had been using are largely out of fashion, so almost no one is bidding on them. As a result, I was only getting a pittance. By changing to the larger, graphics-based ads, I will theoretically be able to get ads that pay better and are more relevant to the content of the page (hence the increase in Netflix ads). For the main site, there has been no change in the number of the ads, just in the size and placement. I have added a couple of ads to the forum headers. (I briefly tried a single ad but it actually looked weird; the presentation is better with two.)
I don't foresee any additional changes, although if the revenue increases enough, I may be able to scale back on some of the other ads. So far, based on a small sample size, it looks like a modest but noticeable bump.