You can count Tarvaris Jackson's completed bombs on one hand. But since I've been to every practice, I can say with confidence that his lack of long ball completions isn't entirely his fault. He throws a beautiful deep ball, but his receivers have dropped some on-target passes. Just now, he had a nice one to Todd Lowber. But Lowber, who had a full step on his defender, flat dropped the ball.
While he's had his issues, Jackson has shown that he does have the touch and arm strength to throw the deep ones.