There's no way to prevent upvote on post people haven't read.
As for the trending page, I think there can be many type of algorithms and many trending page. Communities will also help in that regard.
Obviously the number of votes can easily be gamed so I don't think number of votes are going to be prevalent in many trending algorithm though they might still have their place sometimes.
What ive always wanted was a trending page for different activities , not just a big pile of mashups.
Vids, sounds, zaps, especially zaps should have their own tab they go to.
This would really help in sorting things out, zappl especially would finally be able tl take of.
More than trending page, let there be a separate switch for each major sevices, just like tags, but, i dont know. . . . . . More interactive .