I did it! I managed to be one of the first upvoters (within the first 10) for a post that made trending: Having a son with down syndrome. This post made $5.5k. My reward for being an early upvoter: 0.431 steemit (worth about $1.55, or 0.028% of the take).

Although this is significantly better than the rewards I've seen previously, it's still a comparatively poor return on a few hours of work -- especially when compared against the reward for doing nothing (all I'd need is 40 steem power, or $160 investment at current prices) to accumulate this in interest every day!

This may be enough to entice users in extremely impoverished nations to curate posts, if they're good at it. But for everyone else, I think it actually strengthens the point that there's really no money to be made here (both stand-alone and in comparison to doing nothing), and thus no incentive to participate.