[jlynn]

This leaves me wondering how you might a site like SO that incentivizes participation and quality answers, but disincentivizes poaching and incomplete first answers.

Could you build an incentive strategy and reputation system around collaborative answers?

[vitd]

One option is to either not show scores for some time after answers are posted (at least to other viewers - maybe the asker could still see answer scores?), and/or to randomize the order in which answers are shown for some period of time. That would at least make it less likely that people read just the first answer, up-vote it, and move on. Each person would see a different "first" answer, at least for some time period. Maybe after an hour or 24 hours, then they become ranked by votes? Just a thought - I haven't actually tried it.

[stcredzero]

What if incomplete first answers could be "merged" with better, more complete, answers, with the better answer getting the karma from the incomplete one?