Some people have suggested that the 20% interest rate for the first year is too high. It sounds like a lot, but not all of that will be realized.
Even easier demonstration: investing in just-dice.com will give you that much interest rate. Investing in doge-dice.com wille give you even more (but this will come with the risk of losing money because of falling dogecoin price).
Of course, if you expect mintcoin to get a continous rise, this is different story.