I don't see anything wrong about "breaking up" even if you are not at the end of your rope with the relationship. I don't feel compelled to stay in touch with everyone I've ever been involved with. The same holds true whether it's a romantic/sexual friendship or a less-than-intimate one.
Over the years, there have been people I've made a point to keep in touch with who would return my calls, but would never make the gesture to call me first; I'm even friends with one of these individuals on Fakebook, but I quit reaching out to him (other than the friend-request). He knows so many people (showbiz) that I'm not even sure he knows who I am because I used a nickname most of the time we were together and now I have a married name as well.
Speaking of Fakebook, it has enabled me to get back in touch with a ton of people who I never even would have begun to think about, which is very cool.
But, as far as breaking things off with someone on purpose, or over time, I don't see it as a sad or negative thing in and of itself. Sometimes people's lives just take them in different directions and they get involved in other things. It is what it is.