As another idea you can also look at how Duolingo has developed since it is mainly crowd-sourced. As for the Wikipedia summation contest I would say do it by number of tl;dr's as well as quality and have some kind of cash award for users that post the most with best quality.

I'm no expert on any of this; just a college student with a interest in a lot of things. But growth is what will make or break this as a viable service. Duolingo is successful because it is an incentive to learn another language.

The incentive to summarize something that is difficult is there; but if people are not willing to read the whole thing in the first place then they probably aren't willing to summarize it. The problem is to solve this by providing at least some form of incentive or general interest in it. That requires some key thinking.