I suppose Hubski is follow with a pinch of bump. Pretty good to let user choose what they want.
Twitter is pure follow and time. Relevant for a short , fast newsfeed. Any feed incorporate time anyway.
Reddit is pure vote and time. Vote is prone to manipulation. I dont think it's a good system.
Any forum work on bump. It's as bad as vote. I read some instruction manual on how to manipulate forum by bumping irrelevant contents to bury "problematic" thread. Any bump system should consider how it can be exploited.
Facebook is follow and vote -and, as anything, with time factored in-. It seems to be the more complicated of the bunch. I read here - or on reddit- that they just changed their algorithm so your news feed is less dependent of the number of "Like" -which you can buy, as Upvote on reddit-
I dont remember how Myspace worked. It was just a blog with a pinch of follow no?
Good luck with your system. May be you should try some new system (I cant think of any)
More of an exercise than a system I am planning on applying finding a novel system would be interesting though.