In the future, I hope they partner with hospitals/medicare to provide fitbits for free. There's immense savings in preventative medicine.
A lot of people don't see the potential for movement trackers beyond counting steps. By looking at the data, you can identify when a person is beginning to get sick or weak before they even feel symptoms.
One such startup working on the data problem: http://ginger.io/
What I would really like to see is an open standard for data formatting, similar to the IPC 2547 CAM-X series of standards for industrial equipment output, so it'd be easy for 1) developers and 2) consumers to shop around without worrying about losing their historical activity information. As you mention, this is a serious consideration for everyone, and it's incredibly annoying to feel locked in just because you can't get your data out (or even better, out and then into the next system). A personal example: I really like Runtastic and I have a couple hundred miles logged over the last few months. However, it's a European company and not nearly as popular in the US as Endomondo, Runkeeper, MapMyFitness and a few others. This means I'm missing out on the social aspect, which itself is a motivator. I'd like to try out some other apps, but I can't import my Runtastic data. Argh. (Runtastic is really great, btw.)
I don't like it, and would not participate. Why should someone who is fit and healthy have to carry a tracking chip to avoid a $75/mo fee? Aside from the privacy concern, anyone with 5 minutes to devote to the problem can beat the system.