@timcliff posted a great article on his suggestions for combating voting abuse on Steemit, and there were some fantastic suggestions in the comments to help the cause as well.

I highly suggest reading his post yourself to get a feel for what suggestions he has, but I'll summarize them here (at the risk of missing some of his important points for brevity)...

1.) People who upvote themselves need to ask if it's really "moral" for them to do so, and the best thing for the community.

2.) People who want to combat self-voting need to organize to downvote those who choose to upvote their own spam/poor posts.

3.) There needs to be a monitor of how much of the rewards pool is going towards those who choose to upvote themselves. (Current estimates are at about 10%.)

Valid suggestions...

...but it relies on the community itself to do something about it and sacrifice rewards and self-interest in order to make any substantial change. As @timcliff states, bots like @steemcleaners do a pretty good job at helping to weed out some of the chronic spam and plagiarism. But they're far from perfect and are a "centralized police force," in essence, with limited avenues of appeal in the case they get it wrong.

It's one big entity carrying a big stick, while Steemit was designed for a crowd of people to carry small sticks to knock down chronic spammers, (bad) bots, and people who don't deserve the rewards that they've voted for themselves.

As long as self-voting is possible - which it should be, because if it's not, you're going to get everyone signing up for a second account to upvote themselves anyway - people are going to use their limited reward pool to primarily upvote themselves.

It's largely agreed upon that upvoting yourself when you make a halfway decent post or comment is fine, and the community won't "shun" you for it. It's socially acceptable, for the most part.

What isn't socially acceptable is making a "Great post!" comment, then upvoting yourself with your $1.00+ upvotes, and summoning the upvoting bots to upvote your shit two-word post that adds nothing to the conversation.

In these cases, people should have the right to downvote the hell out of those posts to discourage that sort of shit and penalize those that do it chronically. If you're sending a $1.00 payment to @minnowbooster to get your "test post" upvoted, I want to be able to downvote that asshole to cost them money and prevent them from doing it ever again.

But NO ONE does it. Why?

Because there's an opportunity cost. I need to waste my own voting power that I could use on myself, or the people I follow, or the people that follow me, that actually make a good post that deserve their share of the reward pool. So I suck it up and move on because it doesn't make any sense for me to waste my rewards just to stop a spammer.

You could make an appeal to me that we, as a community, ALL need to downvoting these people. But when no one else is, I'm sacrificing my self-interest and my own rewards to do it, and I'm not even making a dent in the overall problem. Just making enemies that will probably make it their mission to downvote everything I do.

OK, so how do we fix this?

There were a few good comments in the thread that suggested possible solutions to help incentivize people to downvote spammers and those who upvote their own bad posts for disproportionate rewards. A few ideas I thought might be effective:

Post Reply by @liberosist...

When I first joined here, I suggested downvote rewards. Fighting abuse is an important function that should be incentivized - particularly if the same post is then downvoted by others. Yes, I'm aware there's revenge downvoting or spiteful downvoting, but I see that as no different from self-upvoting. Besides, they would continue downvoting irrespective of anything. There's also the issue that the most abusive posts will be downvoted to $0; so where's the rewards generated then? Just a thought experiment. Either way, there should be some incentive for people to form abuse fighting groups.

An interesting idea, for sure. Another good thought by @mattclarke...

We're approaching this from the wrong angle.
Currently, self upvoting is the most lucrative use of voting power.
We can't make it less lucrative (mutual voting alliances, sock puppets, etc); so we need to make curation (the other possible use of voting power) more lucrative.
Give people something better to do with their voting power, and they'll do that instead.
I expanded on this idea here.
(Past payout)

Great simple idea by @attalis, in response to @mobbs assertion that most posts on Steemit are actually spam/plagiarism...

Maybe we can have a spam button and mark spam posts as such.

Here's my idea...

Clone the voting pool into both an upvoting pool and a downvoting pool. The upvoting pool works exactly as it does now. The downvoting pool offers no rewards, it's simply used to diminish the rewards of others for those who are abusing the system and downvoting spam. Just like the upvoting pool, the more SP you have, the more effective your downvote is in reducing rewards. While there would be no direct incentive for downvoting (like the idea by @liberosist) it would free up the rewards pool for those who actually earn it.

More importantly, that would remove the opportunity cost of downvoting others who are abusing self-upvotes and spam, while still making sure that you don't abuse it by downvoting every single post.

While a community-driven solution is ideal, spam and malicious self-upvoting is a chronic problem that will likely not be fixed without a technical implementation of some sort. I'm sure there are a ton more ideas but I just thought I'd throw my 2 cents out there and point out the suggestions I liked the most.

Thanks for reading! Your comments are always appreciated. :-)