I don't have any evidence that would be permissible in court, no. Nonetheless I know a lot of people involved in both worlds (including on the monetization angle) and unless there's a wide-spread, concerted conspiracy to trick me into not releasing an iPhone app, Facebook/Myspace ones monetize at least an order of magnitude better.
Just because your paranoid doesn't mean they're not after you, Matt ; )
Kidding aside, one other aspect to consider is the amount of investment required to get an application released on either platform (the true profit vs. just revenue). A game like iShoot can be put together by a single developer using commodity hardware in less than 100 hours. This application, once released incurs no maintenance cost in order to generate revenue (see note below). A developer can therefore turn out additional applications of this class with little support overhead required.
I haven't written a Facebook app yet, and perhaps a successful Facebook application can be created using the meager developer resources described above. However in addition to initial development costs, as I understand it, the developer must provide the infrastructure to run the application (web hosting, bandwidth, etc.). On an application which receives the volume of users you describe, this can add up to a significant ongoing expense.
You clearly know more and have more experience with the Facebook platform than I do, if I am incorrect in my statements please enlighten me.
*of course you can continue to spend money on promotion and advertising, but since this applies at least equally between both platforms, I consider it implicit.
Using rails and Facebooker we released our first app I think in something like 2 days. We went from 0 platform experience and an idea to a simple but functional app (that grew like crazy, but unfortunately had only 2 weeks to sign up new members) in probably under 20 developer hours. Our following app (the one that is doing fairly well today) took something like 1 developer month to launch, though we've since put probably put 1 developer year into improving it, generalizing the engine and launching two new themes on top of it, as well as porting the whole thing to Myspace. We'll be releasing game #4 onto both networks this week.
We didn't have to worry about being accepted into any store. (Facebook has an app directory that takes a couple days to get reviewed for, but honestly there's very little benefit to even being in it.) After we launched, upgrading was as simple as any website. We didn't have to make some fairly hard to achieve top 25 list to get traffic, in fact, we're hoping for the reverse.
Developing for Facebook isn't that different than any other web development (in fact a lot of apps run in an iframe). It's far easier, and gives far less control to a third party. It's far more lucrative, doesn't have the "hit or miss" aspect of the app store.
You're right about the hosting cost. Only some iPhone apps need that, many do not. All Facebook/Myspace ones do. But the greater monetization potential more than makes up for it if you're doing games (I'm not so sure about other types of apps). eCPMs on offer pages are measured in the $100s. Many people I know (in a way that would be admissible in court) are pulling in north of $500. Even if that only amounts to 1% of your traffic, that's still ludicrously high, especially on the volume you can get very quickly.
The only way in which it is inferior is it isn't sexy and nobody is going to write lots of articles about you. The iShoot guy got more coverage in bigger media outlets for bringing in $600k than Zynga did for making $40-$50m last year.
