It's not inspiring unless it moves people to action. I hope those that wrote on there are on their way to figuring out some way to make their dreams and goals come true.
Of course, it's always up to the person to act but I find it's easier to work toward a goal when my spirits are high and being surrounded by hope has an uplifting effect.
Yes, something like this is easy for people (easier than doing something perhaps). They'll participate because it's there and there's no commitment (you just write things on the wall). But, what of the people who pass by it and, as Dysiode has said, what if it sparks an idea in them?
It may not directly change the world but it sure can plant the seeds that do.
So, I now believe that tiny things like this can mean a lot to someone who's on the edge and can turn them around.