I tried once or twice to edit articles but was quickly rejected by editors that usually believe they sort of "own" the content. I've quickly become demotivated as explained in the analysis and never contributed again. Another problem is that when you think you've made an important and useful update you're never sure when someone will roll it back. Some are spending a very big chunk of their time to make sure articles…
I suppose the problem with that is ensuring that the system 'promotes' enough normal users to fill the gap; again, random assignment might work. Sort of like an online equivalent of Athenian democracy.
People might be keener to be active editors if they receive an unexpected invitation to participate, but with the understanding that it might only last a week.