John Mayer Brentwood Taverna long hair

John Mayer dined with pals at fav celeb spot Tavern in Brentwood Sunday night. And with that T-shirt and long hair ... he was literally and figuratively one big target.

Of course, Mayer doesn't help himself. At a recent concert at Berklee College, he told the audience that he had quit Twitter. "I was a Twitterholic," the singer said. "I had four million Twitter followers and I was always writing on it ... and it started to make my mind smaller and smaller and smaller and I couldn't write a song anymore."

Twitter! The incredible, brain-shrinking website! Alert the scientific journals! Thank you, Dr. Mayer.

At Tavern, our photogs asked Mayer about the Twittincident. Watch his response below.