Hah. I'm a self employed freelancer, but a friend works for (MegaCorp Intl) and every time we go for beers he mentions that he has "Unlimited Paid Time Off". But whenever I ask if that means he could take a few months to hike the Andes with me, he says.... well, no, actually they'd fire him if he took too much time. How much is too much? I ask. Well basically anything that would make them notice his absence, apparently.

And there's a problem in the other direction too - I don't expect people who really can leave for a few months without their absence being noticable to have much job security.