I think a curation trail is great, to be honest. I understand, that it might get abused. But those people are unlikely to benefit as much as everyone else. You can't stop people from being lazy. They might as well get on the "new" page and upvote the top 5 posts twice a day. Bam! Curation done!
Finding somebody you trust to curate daily and hopefully even well, is not easy. I personally feel much more comfortable holding the reins of my upvotes in my own hands. I don't have much time. But I will take the time for this. Not because I'm a romantic, that is afraid of the wrong person getting an upvote. I'm pretty selfishly motivated. I just like to be sure, that I have my minimum of ten upvotes, when I go to bed.
Also it's a great motivation to keep reading, what's going on at POB and hopefully get some inspiration to write something interesting myself.
Find a group of people who constantly write about things you enjoy reading. Problem Solved. Having a hard time finding a group of 10 people? Make a post announcing you have stake and that you're looking to read content of a specific type, asking that people who write about it say hi... That's all it takes.
The first problem with 'banning' the use of curation trails (or any type of auto-voting) is that it is currently impossible for the blockchain (and thus the community) to know the difference between an auto-vote and a manual vote. However, this could be fixed through the front-end, if we require a 'captcha' style confirmation with each and every upvote -- that does diminish the user experience somewhat, though, and that would require upvotes ONLY be cast via the front-end.
A much bigger problem, though, is exemplified by this comment from @antonym:
If a stakeholder is using one or more curation trails, that means he/she is trying to at least indirectly contribute to meaningful curation. If you take that away, you inadvertently incentivize random manual curation that muddies the curation waters far worse than curation trails.
I disagree. Stacking votes on good content would be the most optimal choice. In fact, it would be that much important. Not to mention, voting on random people means they will sel all the POB they get, which would be bad for large stakers.