Someone who doesn't want the coin to grow up can send the minimum amount "0.00001 XCN" plus the fee "0.0000001 XCN" to 1 BILLION addresses to increase the tree size and that only costs him 5.81 $.
That's why it's needed and I'm sure you understand that as you "the developer" is the first who suggested it.
I am the creator of the mini-blockchain scheme, not the developer of Cryptonite. And I believe the original Bitcoin code has some safeguards against that sort of activity but you do have a valid point and that is one of the reasons I suggested it. I just don't really think it's worth worrying about until there's actually a reason to worry about it, because there are far more important things that need to be done first.