Yes, Android might be "open" in the sense that the sourcecode is available, but there's no doubt Google's wielded incredible power over the platform by restricting access to Market and its own apps -- power that hasn't been used to prevent carrier-mandated bloatware or poorly-done manufacturer skinning, but has instead apparently been used to block legitimate competitors like Skyhook from doing business.
The gamut of possible outcomes runs from a mild go-forth-and-sin-no-more to the truly Draconian stuff: forcing Microsoft to share its Windows sourcecode with its competitors or carving it up into separate, independent companies, the so-called Baby Bills (see chart).