At the free sample counter at the grocery, or grabbing swag at the trade show or clicking like mad to suck up free content online–people are at their worst when they're in a free frenzy.
Sure, free is a fine way to grab attention, but more and more often, it's precisely the wrong sort of attention from the wrong people.
I'd much rather work with someone who says, "what have you got that's expensive… but worth it?" Not because that person is about to pay money, but because that person is focused on "worth it."
The people at the samples bar at the supermarket, or the free downloads section of the web, aren't asking that question.
When looking at free, the 'worth it' question never comes up, because when seduced by the zero price and nothing but the zero price, we fail to answer the question about worth or value. Sure it's free, but is it worth the price in attention, distraction and quality?