Why does that make me happy?
I used to read several "green" blogs. Eventually I stopped because I got really sick of the blogs advertising all these green products you could buy, mostly for very high prices, and rarely ever reminding people "But actually, buying new products, even green ones, isn't as good for the environment as not buying new products."
So I think the sign is a good reminder: "Hey, if you buy this thing that someone already made, it's better than using up even more resources to buy something brand new."
And it's a clever form of marketing. (Well, in theory. I haven't actually bought anything in that shop, and I don't even remember which one it is. I just smile when I drive past the sign.)
While I'm on the subject of reusing things, I'll put in a plug for http://www.freecycle.org/ — another way to get things that someone already made into the hands of people who will put them to use. It's an organization that supports a lot of local mailing lists where you can post that you are giving something away or that you want something. I've had both good and bad experiences with my local groups—mostly reasonably good.
Some of the folks on my friends list talk about barter, which also seems like a good thing. I've never done it myself except for informally with friends.
What are your experiences with freecycle / barter / other ways of redistributing things?