I will add: the knee-jerk reaction to this is everyone will self-upvote with 100% of their SP, However:
If you are able to commit a significant amount in curation, you basically get 25% of the follow on rewards. So you can easily do better by curating good content.
Being selfish may not be the best strategy, building a social network by up-voting your peers might be far more profitable than 100% up-voting.