Key Points:

The CNN hologram during the US presidential election bought the news network a wave of positive publicity.

But the fizz has gone out of the much-vaunted new technology as bloggers and hologram experts lined up today to point out that the holograms were, in fact, not really holograms.

PC Magazine blog, Gearlog, pointed out that "CNN's Holograms aren't Holograms: So Cut it Out."

"There was no live, glowing 3-D picture that people could walk around," wrote analyst Sascha Segan.

"The 'image' of Jessica Yellin and Wolf Blitzer standing in the same room existed only on TV screens."

The remarkable thing, he said, was that CNN could make the images look so real to viewers, while the presenters were speaking to thin air in the studio.

CNN billed its hologram technology as a world-first beaming in reporter Yellin and rapper from Chicago.

But, in the studio, presenter Wolf Blitzer was looking at just a red mark on the floor.

Critics have pointed out that Blitzer tried hard to make it appear the hologram was real.

He told thin air: "Jessica, you're a terrific hologram."

He went on to praise the hologram because "we can have a more intimate conversation" and Yellin said she was like something from Star Wars.

Later, there was a second hologram interview between anchor Anderson Cooper and