A specific example
For example, I've done several drops for a woman based in South Perth. Most of them have been in that suburb and in neighbouring ones like Como, Kensington and Victoria Park. She always got a better response from those areas. Of course, this was partially due to those suburbs being quite comfortably off, and able to afford what she was offering (weight loss hypnosis). But the repetition helped a lot, I believe.
After having really focused on those areas I then did a couple of thousand in Innaloo. No calls from this suburb, at least as far as I know.
I think this was mainly because these people had just never seen her ads before. Those in the South Perth area had been exposed to them repeatedly in the past and so noticed them again.
Clearly, persistence pays
So it can take a while before you actually get on the radar of people. That's why it's good to keep doing them over and over again. Although of course, you don't want to repeat drops too soon. Do that, and you can end up annoying them!
In this need for repetition and persistence, offline marketing is a lot like the online kind. In both methods, you just have to to keep appearing in front of people. On Twitter, for example, persistently logging in and tweeting really helps a lot. Firstly, you get more followers that way. Then you start to stand out in the streams of those following you. You've appeared so often they actually know who you are. Then if you tweet a link to one of your blog posts, for example, they're much more likely to click on it.