ice damns are 100% caused by inadequate insulation and lack of/improper attic venting....put your money there. If I were strictly in the insulation business I would spend part of my winter time driving around taking pictures of houses with ice dams and then contacting these folks come spring to try and sell them a solution to make the problem go away and save them money year around.
I don't think "100%" of the cause is "inadequate insulation and lack of/improper attic venting".
I will agree that having adequate insultation and proper attic venting is very important in reducing ice damming and long icicles from the eaves and gutters; but you can't eliminate ice damming in many situations.
Some amount of ice damming and icicles from the eaves and gutters is an eventually anytime you get snow on the roof and your have right atmosheric conditions (temp and sunlight).
Scenario: Lots of snow on the roof. Lots of insulation and great ventiliation. Outside temp is 28*F and its sunny; not a cloud in the sky.
Eventually the sun will warm up the roof (especially if the roof is a dark color) and the snow will begin to melt. The water will run down past the outside walls of the structure, over the overhang, and into the gutters. The roof beyond the outside walls of the structure and the gutter will be 28*F (same as outside air temp) and the water will freeze. First in the gutters blocking a way for the water to "get away". Then an ice dam will begin to back up the roof. Eventually the water will flow over the ice dam, over the frozen gutter, and start to create long icicles.
The snow on the roof eventually will melt and turn to water. Gravity will take it down. The outside temp when the snow (and ice) melts will dictate whether you'll have an ice dam and icicles, or not.
Really low temps (low enough that direct sun on a cloudless day against a roof doesn't get the roof temp to 32*F) should not be a problem; no melting. The snow will start to sublime away.
The problem is when temps are between about 26*/28* and 33*/34*. Just high enough for the snow to melt in direct sunlight, heat the roof up, heat the attic up ... but freeze the melted snow (now water) when the water gets away from an artificial source of heat and is cooled by the outside air.
Above 34* outside air temp and you shouldn't have a problem ... unless you already have a really good ice dam built up. It will take a while to warm the ice dam up to doesn't freeze the water running over it and actually starts to melt itself.
I think that gutter guards and stuff like that only compounds the problems in the winter time. I believe the only solution is to have the heat wires in the gutters and up the valleys to create a path for the water to get into the gutters as water, not freeze, get down the downspout, and onto the surrounding ground.
I await constructive feedback.