I see no problem with trails as long as they are voting on posts that are good. There are some scammy "circle jerk" type trails that exist as well, which are obviously to be avoided if any integrity is to be maintained.

Oh yeah, we don't have to look far. This becomes even more of a problem down the line when there are only those trails that can sufficiently reward posts (look at Curie, OCD etc), and I say "sufficiently" very loosely. It all starts at the beginning, it's no surprise why some accounts run away with the stake size and then everyone below has to nip at them for a little drop of "feel good juice".