no specifics have been released but in the q&a Igor made it clear that masternodes are able to affect the network stability in both good and bad ways.

I believe the bad way could be that  there are too many masternodes coming and going because 1. you don't need a lot of coins to start one, and 2. because they don't give enough income. That's why I believe the minimum amount of coins will probably be over 50K. They're not going to want small bag owners starting masternodes only to sell their bags again because they're barely making a few dozen sonm a month. The incentive of holding a masternode is the passive income, but if that's neglectable, people are going to sell their bags when prices go up, which results in the network not being stable.