As stated before warm up of 2+ minutes is bad due to wasted fuel and pollution. Comparing it to other activities that also waste fuel and pollute air doesn't make this practice any better.
Although this winter has been mild, up here in Canada I would generally face -10C to -20C in the mornings so cold starts concern me. My solution is to focus on other methods that can reduce engine damage so that I can idle for no more than 2 minutes at the most and go.
1) For myself (driver) I simply put on extra clothing, gloves, etc. I gave up on heaters and other gadgets. The point is not to expect the car to heat you from the moment you start it, but use some extra clothing. As the engine warms up and starts heating then you can take it off.
2) As the UOA above shows and many other discussions explain, today oils are very good and can deal with acids, fueld dilution and other issues very well. Therefore, I simply use a higher quality oil in the winter.
That means going full synth, such as Mobil 1 and use a lower grade that is easier to pump at low temps.
My Hondas recommend 5W30 year around, so I will go to 0W30 and mix in some 0W20 or 5W20 for winter. Due to the lower tempoeratures engine will never reach higher temps as in summer. Since I don't go on longer trips I think the lower grades will be just fine, yet will pump better on cold mornings. That way instead of idling 5-10 min, 1-2 min is plenty.
So I think some idling is necessary, but using the appropriate type/grade oil you should never have to idle more than 2 min, maybe 5 min in extreme conditions. There was a note about frozen windows, in which case I cannot go even if engine is warm enough as I cannot see. So I might need an extra few min and even then I will start and drive slowly on the local street until I can clear the freezing rain from windows.
So use a lower grade oil and more clothing and you'll be fine.
