As much as Web 2.0 ideas are about openness and freedom, they indicate an increasing emphasis towards power and heirachy. You can see this directly manifesting in the present situation of Yahoo! swallowing Flickr and the precarious dynamic between del.icio.us and Google, which makes me think of the core system of control being not so much the data access, but the bandwidth itself, the physical business of information flow.
When viewed, intertwined with the whole dynamic of global capitalist markets, there's really not much that is surprising or strikingly different about this web from other forms of media, especially considering the way public APIs operate as an explicit contract between consumers and producer. Many have lept on the core business philosophy of Web 2.0, organizing and optimizing these bindings - as William Blaze points out, this is not actually letting go of control, but "controlling just how you let go.".
It's certainly worth considering how the Web 2.0 meme conveys a certain qualitative shift in basic thinking about the web and what is possible. If there's any particular power grab going on, it's a power grab by the open source movement, pushing ever further, trying to validate their approach and reach that elusive mass market mindshare. And within this same space, there's an interesting intersection with ideas about enabling a writeable web. The point is that control is always limited, and these limits are a basic part of the system's design. It's possible to screen scrape information off public web pages just as effectively as tapping into an API, but there's no centralized control or data design beyond the basic syntax authors use to markup their web pages. This is a much more anarchic approach to data, perhaps in line with the original goals and philosophy behind the platform of the web itself...
The idea was that anybody who used the web would have a space where they could write and so the first browser was an editor, it was a writer as well as a reader. Every person who used the web had the ability to write something. It was very easy to make a new web page and comment on what somebody else had written, which is very much what blogging is about.
As web platform innovation becomes increasingly centralized, there will always be people enthusiastic enough to exploit these platforms with decentralized technologies. As long as HTTP and HTML remain as basic plain text, the web will remain a global, open medium, where knowledge can be universally referenced and transferred across open channels. One of the basic tenets of this form of organization is that the user should always have control - not just over the locations they view, but right down to the basic look and feel of the user interface. Historically, Greasemonkey stands ahead of a whole line of default formatting preferences and stylesheets that go back to the very beginnings of web browsers.
Good software enables good publishing, and good publishing requires a certain level of discipline to succeed. Asymetrical power relations emerge with the ability to aggregate data en masse, to filter, summarize, redirect, simplify, and map. To me, these terms of control seem like they translate directly to bandwidth, plain and simple. This clustering of bandwidth enables certain organizations and insiders to have a phenomenal impact on peoples perception and usage of the web but as much as this centralization feeds back and influences the web itself, centralized data is often highly dependent on the widely accepted standards that individual publishers themselves adopt. It would be easy to say that anyone can lay down the building blocks of the pavement, but only a select few have the power to manage and direct the mass traffic. That's true to a certain extent, but ignores the basic fact that in many parts of the world, just having access to the web is a privilege in and of itself. Still, theres no doubt that everyday around the world it becomes more ubiquitous, and this process of opening up new markets and potentials has given rise to a strong tension between free flowing communication and cultural domination: "These are of course the same classic problems of the management of a large organization, of combining individual creativity with corporate vision." Interestingly enough, in such top-down utopian thinking about the early web, it's not the word freedom that comes up time and time again, but the word flexibility. As an HTTP addict, I see it not just as a protocol, but as a philosophy, a discipline, a way of thinking about distributed architecture. The main split in my thinking about Web 2.0 is how making web pages rewritable, mashable, remixable in browser fits into this bigger picture of ad hoc integration.