When new user enters an idea, or votes for someone else's idea for first time, he just presented with option to choose from "1 votes", "2 votes", "3 votes". It can be confusing what this actually means. On my feedback forum most users give just 1 vote for their only idea. I suppose this is because they don't understand they could give it 3 votes to have better chances for their idea to be on top in overall list.
There is also no mention (until you register) that you have 10 votes that you can distribute among ideas you like. I afraid some users just don't understand the idea of how those votes work.
I like the simple interface design, but there are should be some hints, especially for new users.