Tough question. I can't remember the last time i harvested a wild trout. Pretty much the only time I will keep one now is if I don't think it will make it because it was hooked deep. That said, I am not a die hard C&R guy. I am an apex predator, and who says that me eating a trout isn't natural. I say it is. Keeping a few doesn't change the population one way or the other, long term. I guess i throw them back simply because it feels right. Plus, I like a natural experience. Eating a few is a natural thing to do if I chose to. Keeping a few to try and manipulate the population, isn't natural. It just doesn't enter into my decision. Well, at least not much. ;-)
As far as what Jay says, I don't disagree with it.
I believe you can manage a stream for larger size trout but it involves harvest. It can be done in my opinion, but is it worth it??? It is true that the biggest limiting factor is their environment. Left on their own, the average stream that I fish for wild trout (Small Class B,C, or D freestone streams) just simply can't produce many large trout. There isn't enough food for that. However, if you reduce the number of trout, that leaves more food for the ones that are left. Less competition. It most definitely works in ponds. It just wouldn't be easy to do this on a trout stream for several reasons. Besides the obvious reasons, most people would still throw them all back (including myself). Then you will have a small number of people who would still keep the largest ones, and it wouldn't take many people to screw up the plan. Even if you were able to manipulate the population over a couple years to get a more desireable result, you would have to stay after it constantly to keep it that way. It aint natural.
Keep in mind ... I'm just commenting on the typical streams that I have fished. They are actually easier to screw up short term than they would be to make better long term, so please don't try this at home. :-D Limestone streams are a whole different ballgame and I am not commenting on those.