Wow, paying Twitter bots to get more community rewards is horrible. I'll admit I'm not too active or engaging on Twitter, but some people are. I just post my blog because it's another index and good for SEO.
Nomination trading is the phrase I was looking for. I'm guessing you will know how to tackle it if this becomes a problem.
Since becoming active again, I've noticed engagement is still surrounding a few focal points. Most of the focal points definitely deserve it, and you can't stop people from chasing money with reasonable effort and honesty. But, I really hope to see a lot of activity and success all over the place.