Well...I definitely don't do this. What I mean is, I just look for segments that are around where I want to train, and plan the route around them. If it's my Thursday fun ride, or maybe my Tuesday sprinting day, I'll meter my efforts so that I can go particularly hard on those segments and see how I do.

The real value in this approach is that generally well-traveled segments are also on roads that are good for cycling, so I get a little local insight into some potential new routes. I like to avoid heavy traffic, for example.

I ignore all downhill segments though, and those that require running stop signs. There are quite a few of those, and it kinda makes me wonder who's taking such silly chances for something so pointless.