The major broadcast television networks are blocking their content on Google TV. They are blocking Google TV because it is putting a web TV show, with web TV show economics, on a TV, which would be incredibly disruptive to their business.
The reason the networks are blocking Google TV and Boxee (and Hulu is still PC-only) is about ad revenue: they don't get enough of it from the web. And letting you watch "Glee" on your TV, but via the web and Google TV, means substituting high broadcast revenue for lower digital revenue. Ultimately, the networks would like to either normalize the number of ads on the web and TV or increase the revenue per viewer-minute on the web through new, targeted or interactive ads.
So far, networks like ABC, CBS and The CW have been increasing ad loads slowly, as the market and viewers will support it. Nielsen and others have systems in the works where the networks could measure or sell audiences across both TV and the web -- if the ad loads were the same. Once there is parity on the revenue per viewer per minute, then you will see web shows on Google TV or Boxee, and Hulu on your TV set. Until then, though, the networks will do everything in their power to keep TV shows distributed on the web on PCs and TV shows sold for TV on the big screen. No conspiracy of old media to stop technology or thwart user choice here; it's a rational business strategy, pure and simple.