Details of 3D TV
It's Stereoscopic, not 3D. A separate image is somehow sent to each eye. Glasses (Polarising, synchronised LCD shutters or coloured filters) usually need to be worn. The non-shutter versions don't work at all for anyone with a lazy eye and possibly up to 1/5th of the population. Even the shutter version will cause eye strain for maybe 1/4 population. Stereoscopic so called "3D" first used in Cinema in 1930s and in Victorian toys. Viewmaster is the 20th century version still sold in toy shops.

It's greatly overstated the degree of 3D illusion. Do buy a Viewmaster (Argos? Smiths? Tesco? Toys dept) to get a perfect idea of the degree of 3D being offered. The view is the same even if you move your head or position. It's simply a depth illusion which varies according to the matching of your eyes. To offer it at the same quality as ordinary TV, you do need twice the disc storage or transmission (except for the poorest Anaglyph method, so most systems either halve the resolution (Polarised or Lenticular/Autostereoscopic) or use alternate frames (LCD Shutter).
Stereoscopic Methods (So Called 3D but not actually 3D)

  Sky HD 3D broadcasts are actually "Stereoscopic" not 3D at all. The Anaglyph method is little used except for cheap glasses and novelty Broadcasts, VHS and DVD as although it works with any Colour TV set, the quality is poor and stress-full.

Stereo Viewing is a poor 3D illusion even for people with evenly active eyes. It can be stressful and the Glasses may be uncomfortable or interfere with glasses you need normally for TV viewing. See also http://en.wikipedia.org/wiki/Stereoscopy and http://en.wikipedia.org/wiki/3D_television

Sky will be launching a "3D" channel in 2010. It will actually be Stereoscopic rather than true 3D and require a 3D TV set on the Sky HD+PVR setbox. It's not clear at present if it uses the Polarised system or LCD Shutter.

Conclusion
It is technically possible to have limited viewing angle Stereoscopic screen without special goggles/Glasses, but seating positions are very limited and you have to keep still. The most practical system with an economic priced screen that works for ordinary TV also is the LCD shutter method, which is the only method that has any chance of working for those with less than perfect binocular vision (slightly lazy eye). You still reasonably matched eyes and there may be an issue of how to wear the "3D glasses" as well as your regular specs. It's very poor value for money. Real 3D TV is some years away.

It's possible also to have true 3D display, but the display is very bulky and not very large. It also needs 100 to 1000 times bandwidth for HD at a reasonable depth and screen size, so we won't have proper 3D TV for some time.

Some examples in 2009/2010
Sky switches on 3D TV channel in 2010 This likely using LCD shutter glasses or Polarised Glasses and a Special TV set. It's Stereoscopic, not 3D.
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C4 to have a Week of 3D TV. This is the worst system, Anaglyph or two colour glasses.

Unlike Sky's HD+PVR, the Sagem Sensio is specially designed for HD Stereoscopic TV. The preferred method is LCD glasses.

But it supports all four methods outlined above.

Panasonic BD "3D" system uses LCD shutter glasses.

Philips have the "Special Screen Lens" TV, no "glasses" needed (4th method), but it has very narrow viewing zones. But they have no plans to sell it. They have outlined all three realistic Stereoscopic TV technologies, but are sceptical.

LG have the LCD shutter type "so called" 3D TV.

Sony's offering will be integrated to BD players (BluRay), PS3 and uses LCD shutter glasses/Goggles.

Finally shortly Sony will be demonstrating shortly what might be a real 3D display, if so it will only work with PCs and game consoles as there is no live camera system, nor bandwidth to send true 3D images.