Well, it worked once...
From the Borowitz Report:

Olympic security officials in Athens, Greece conceded today that they had failed to notice a giant wooden horse that had been wheeled to within meters of the Olympic stadium sometime late last week.

The sudden appearance of the gigantic horse, which was said to measure over one hundred cubits in width, has raised fresh concerns that the security around the Olympic complex might be more porous than originally thought....

But Thanasis Kyriakou, who is coordinating the security efforts for the 2004 Olympics, said that the horse, while of unknown origin, posed no serious security threat to the Games, which are set to begin in three days....

For his part, Mr. Kyriakou believes that the enormous horse could enhance viewership of the Olympics and has even recommended wheeling the mysterious wooden structure into the stadium itself.

“I say let the horse in,” he said. “What’s the worst that could happen?”