I have to prune my tomatoes. The wind in Wyoming can get quite high; I heard once this summer that we made hurricane strength, but I don't know how high that is. It can also occur in sudden, violent bursts. One perfectly calm day I was out minding my own business when a gust of wind exploded and dissipated, all within the space of seconds. Thwack! I was almost felled by a three-foot long healthy branch of the neighbor's tree hitting the back of my head. Even though it hurt, it made me laugh. I whirled around to face my attacker, and there was a branch lying at my feet
That said, any Wyoming plant over a foot tall needs to be supported in some way. I use tomato cages for my tomatoes. I space my tomatoes 30" to 36" apart. As they mature and put out new branches, I feed the new branches up into the cages. Eventually, the center growth becomes impacted, and the inner growth suffers from lack of air and sunlight.
So, I prune. Like Cynthia_H advised, I never take more than a third of a plant at a time, but I will tell you that my previously lush tomatoes resemble plucked chickens when I am done. Yes, they also concentrate on production. However, my reason for pruning is not so much to enhance production but to provide support for new branches while making certain the inner plant's vital machinery stays well oiled
One note: If you over-prune, as I do on occasion, you will stress your plant. Earlier this summer, I pruned one of my guys to the nth of his life. The next morning, he had blossom drop. I've left him alone since, and he has yet to regain his full glory. The other four, however, have been pruned at least twice, and two are ready to be pruned again.
Confessions: I might like doing it too much.