It's not complicated enough. Make it log(x)
trickle_down and add random selection.
j/k
those on Depth 2 in your custom list (so those people trusted by the people trusted by the people you trust!) would now need to be trusted twice by those on Depth 1 in your custom list.
I think you're off by 1 level. Users you put directly into your trust list are depth 0 for you. Instead of a trickle-down I would recommend setting depth to 0 and manually adding those whom you trust from deeper levels.