We often use the term red herring to mean an issue which we thought was important, but which turns out to be a non-issue. So, in the end it proved itself to be a distraction, rather than the main event. It is normal to have lots of Red Herrings come up in design and implementation phases, and even during problem analysis. Indeed, if none come up, it probably means someone isn't doing their job.
According to Uncle John's Dictionary of Phrases (from Uncle John's Bathroom Reader)
Meaning: Distraction; diversionary tactic
Origin: Comes from hunting. When herring is smoked, it changes from silvery gray to brownish red and give off a strong smell. Hunters use red herrings to train dogs to follow a scent... and, by dragging a red herring across the trail, they can also throw a dog off a scent.