I've talked with a veneer buyer who says the cause of gum streak in cherry is an insect infestation. This is usually due to logging from early spring to mid-summer. Logging slash is ideal for the bugs' nesting sites. They then go and overwinter in the residual stand of cherry, attacking the bark, and causing gum streak. He said he could go back on an infected tree and predict the last logging occurance.
Bugs are also the cause of sugar streak in hard maple.
I find this explanation interesting. I live in NE Illinois in an area which has wetlands mixed with island-like patches of oak and hickory. There is a fair amount of cherry mixed in with the oak and hickory. Many of these areas have been overrun with non-native plant species that cover the forest floor and kill off the native plants. It is in these areas that I have noticed that all of the cherry seems to be diseased and gummed up.