Let's say you are a whale with a $20 upvote. Let's also say you run a vote buying/selling service. You can upvote yourself for $20, and you can buy votes from your own service. The majority of the curation for the bought votes will flow into your pocket, and you can charge a premium for your service as well, paying vote sellers 85 cents on the dollar.
The more stake someone has, the easier it is to manipulate the mechanics of curation.
I don't understand the reasoning behind, "People would be less motivated to even vote." It makes no sense. Why would they be upvoting other people at all then? Why not just upvote yourself if all you care about is the reward? How is 25% curation any different than simply upvoting yourself once every 4 votes?
Financially, curation is different in that the 25% could be 25% of much more than you could get from upvoting yourself.
Good catch. Yes, the curation mechanic creates a kind of lottery where you can actually make more money than a full vote. However, I have tested it, and at my voting strength, I barley make more than a full vote on posts that get vote botted up to $1000.
The real way to capture curation rewards is to have massive stake. If you are a whale you can capture the lion's share. I think this is dumb, because anyone can see how much a post is paying out. Whales have little curation intensive to upvote posts that already have upvotes.
Also, what is curation? Curation means you get paid to sift through bad content to bring the good content to light. Literally anyone could be doing this, but the way the system is rigged only whales get paid for it. Why does Steem think that whales are better curators than plankton?
I maintain that the real way curation should work is through resteems. If you upvote a post because you clicked on a resteem, the person who resteemed that content should get the curation reward. This makes way more sense.
I've seen the motivations for much voting driven by curation rewards, not by the content itself. Not to say it's all that way. It would be interesting to see how behavior changes on the platform with no more curation rewards. I'd like to see it.