Random thoughts that spring up:

1) If DRK goes to, say, 10 bucks a coin in the mid-term, we are talking about 10.000 usd for running a node. It could be too much.

2) 10% of the mining for last node sounds too much. It also may open up a window of exploitation and give incentive to DDOS in master nodes so that one node takes the fee instead of the other... Other types of exploitation for getting the mining reward could spring up as we go along.

I think it needs to be less, both for the running node, and the mining reward. It'll still be a good incentive + drive the price up.

Something else: The other day someone mentioned about the DRK allocation to various wallets and that Cryptsy has something like 400-500k DRK (?)... so, in this scenario, an exchange of that size can create 400 master nodes as a way to gain "interest" on their money despite the hot-wallet risk. Even if they only used 50% of their DRKs, it could be 200 nodes - which would be a sizeable part of the network under control of only 1 party. That would require quite a lot of laundering depth to avoid the chance of hitting a cryptsy node every single time.