Love to see where you got those numbers from.
That's a generality. Some people lose interest right away and it looks like a exponential function going down. Second, there were no numbers on the graph, besides the months, which are pretty agreeable.
Others may never lose interest with the game or ever fall into that depression. There are several problems why most people experience these "depressions" (so to speak).
1) Teach the community to not discriminate by ID. We could be throwing away perspective "Ostinyo's", "Phydeaux's" and other influential mod creators we know today.
2) Teach people to use interesting building techniques. We want people to be encouraging, and we want to make that an easy job.
3) Teach the community to be positive and helpful to newcomers. What's wrong with being a good person?
4) Show people the diverse range of servers and mods that are available, and recommend creative ways to apply them.
5) Keep prospective players on track by keeping their interest in the game. With more active players playing the game, more word gets out about Blockland.
Try to disagree with any of these and tell me how it would not be a good thing to have any of these.