Beyond the military fight along the border between Afghanistan and Pakistan, the CIA has for years engaged in an aerial war against suspected terrorist targets inside Pakistan using missile-armed Predator drones.
Since September, the CIA has substantially increased the number of those missile attacks, and some have successfully targeted senior al Qaeda operatives. But bin Laden remains an elusive target.
"If we did find bin Laden, it would be more out of luck than anything else," said Baer.
In late 2001, bin Laden was nearly captured in a battle with U.S. forces near Tora Bora, Afghanistan. However, the U.S. has since lost track of him, believing he is now hiding somewhere in the remote region around the Afghanistan and Pakistan border.
"Anyone familiar with the Afghan-Pakistan border area knows how rugged and inaccessible it is," CIA Director Gen. Michael Hayden said Thursday.
"Beyond that remoteness, the sheer challenge of surveying every square mile of that inhospitable and dangerous region, part of the explanation for his survival lies in the fact that he has worked to avoid detection," Hayden said.
Former senior CIA official Michael Scheuer, who led a special CIA unit whose mission was to hunt bin Laden, argues it's unlikely the al Qaeda leader will be caught. "We tend to forget that he's been at this for 25 years," Scheuer told ABCNews.com. "He's quite experienced as an insurgent in terms of not being found."
The U.S. government has offered a $25 million reward for information leading to bin Laden. But Scheuer points out, despite the fact Afghanistan is one of the world's poorest nations, no one has claimed the money.
Scheuer is convinced bin Laden is alive.
"He lives among the Pashtun tribes, and they have a tribal code of conduct that, once you accept someone as your guest, you then have to protect them with your life," he said. "And so there's very few people who are going to turn over Osama bin Laden."