It depends. The tagging system might work out great. Say on Reddit there is r/programming and r/programminghumor (or r/programmerhumor), here you can just have a post tagged with #programming #humor or #funny and it would lead to the same thing. I am sure that as long the moderators do a good job at moderating and not feeding the trolls, there won't be much problem.
To expand on pigferret's response, moderating a subreddit is a notoriously time consuming and thankless job. As a result, very few subreddits are properly moderated. In short, if hubski grows large enough that moderating any discrete part of it take more than a few minutes per day, it is far from a given that moderators will do a good job.
You bring up a point - I can easily see people abusing the tagging system to just slap commonly followed tags on their stuff. #funny #humor #atheism #kittens #followthis #OHGODWHYWONTYOULOVEME
The author is only allowed to add one tag, the followers add the rest. See here. I'm not sure I agree with it, I think the author should be able to add at least 2 or 3 tags per post.