He can't believe his own popularity ...

David Beckham is "amazed" by all the hoopla over his newest underwear ads for Emporio Armani, he writes today on his blog. A giant billboard of his topless torso was unveiled last week on the side of Macy's in Union Square, San Francisco, followed by an appearance where the soccer celeb signed autographs for a few hundred lucky fans.

"To be honest, I was amazed by the huge billboard poster outside Macy's department store, but even more amazed by the amount of people who turned up to see it!" Becks writes. "I'm always surprised by the amount of attention certain things create, but the attention this campaign has created is pretty incredible."

David has spoken previously about his shyness in posing for the ads, telling "Tonight Show" host Jay Leno: "I was quite nervous because obviously I knew my wife and friends were going to see it," he said, adding, "And my mom was going to see it."