From what you suggested, the biggest issues are:

• voting bots
• spam comments
• people begging for votes/follows/resteems

As I mentioned it before (and maybe it was a comment on your other post), a higher quality content gets currently lost in the ocean of many posts that literally waste the resources. While there is no way to get rid of such posts, it would be a great to be able to, for example, easily add users that I follow into groups by categories or at least bookmark the favorite ones.

The line between spam and promotion is, I believe, when the content has a real chance to provide some value to the users reading and/or commenting on the particular posts.

If I promoted my book about startups in this answer, it would be more of a spam. If I promoted a bot for Steemit that would automatically identify spam comments (this is just an example, I don't have any), it would be a relevant promo.