If you use the same mentality that this industry has and apply it to any every day application, you can see the amount of free samples given out is ridiculous. It would be the equivalent of going into your local grocery store and having someone hand you a half a loaf of bread in HOPES that you'll buy the rest of the loaf of bread. Sure, you'll make some sales, but, lots of people will take your half loaf of bread, go make a sandwich and come back next week for another half loaf. Giving away only a half piece of bread, curiosity if nothing else is going to sell more bread than anything. People want another taste. When they come back, you have to turn them away and say, "No, I'm sorry, you've already had your sample. Now you'll have to buy the bread to have another taste." You only have to be sure that the bread is tasty and fresh.
If it's quantity of bread that you're trying to focus on, then put a big stack of bread behind you as you're handing out the free sample, but don't let a consumer take a bite out of every loaf of bread in that stack. Noone's gonna want to pay you for your bread if they can get full off the bites you're feeding them.
Sorry I was bored and on ICQ talking about the amounts of free porn given away. Happy Thursday...