I think there is just too much greed all around. Look at the channels some of the other STBs have. Some have many more than the ATV why? Why has GoogleTV been blocked by the major TV stations? Then on the PC side there is PlayOn which from my understanding sits in a gray area of the law. Roku had to pull official support for PlayOn because of some stupid legal crap and PlayOn says they aren't doing anything illegal since they are only supplying a path for the content and not changing that content in any way. Why should this be a gray area? Too much greed. And if Apple ins't just using the ATV to promote iTunes then why is it only 720p? If they were really just a hardware company looking to make the best hardware then it would have 1080p for all the other content that you can get not through iTunes. Hopefully Corperate will realize the money is in having the content in fornt of people not in the transmission of that content.
Of course greed is involved. It is a business, after all.
As for you questions, here are my opinions.
1. Why do some streamers have more "channels" than others? It really depends on the overall business model of the device manufacturer. Roku doesn't sell content, so it makes sense for them to have as many content partners as possible. Apple sells content, so they need to be careful not to impact one of their own revenue streams.
2. Why has GoogleTV been blocked? Most likely because they haven't made deals with the individual content owners or providers. For example, much of Hulu's content is contracted for playback on computers only. Since GoogleTV is primarily connected to TVs, Hulu is likely bound by contracts to block it. I believe this is the reason that Hulu Plus doesn't include everything that Hulu has.
3. Why is PlayOn in a grey area? I don't know too much about this, but I would guess that the content owners are relying on the provision that end users are not allowed to rebroadcast commercial content. This is a little flimsy, since that's technically what Sling does and that's not been shot down. I will admit, I'm not too knowledgeable with PlayOn.
4. Why is AppleTV only 720p? I don't think anyone has denied that the aTV isn't a promotional tool for iTunes. It is. But there are technical reasons that the device is limited to 720p. The infrastructure in the US isn't quite there yet to support full 1080p streaming and downloads. Plus, they would probably have to put more Flash RAM in the device for a pleasant experience. BTW, the aTV is fully capable of playing 1080p content ... output is still limited to 720p though.
As for your last statement, I feel that the real money isn't in getting content in front of people. The real money is being able to charge people for content multiple times. For instance, if I own a popular TV show, I can charge advertisers on the first run. Then, I'll charge consumers on DVD sales. I can also charge some consumers for digital downloads. In a few years, I'll charge syndicators a decent amount to show my stuff 5 days a week.
Look at Seinfeld. It was a top rated show for years and they collected a lot of advertising fees. Folks are out there buying DVDs. And it's been in syndication for many many years. Jerry raking in the dough and so is everyone along for the ride.
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Holy thread revival!