We know that fluorescent lightbulbs are better than incandescent lightbulbs. But does that mean you should throw out your perfectly good incandescents, or just replace them with fluorescents when they burn out? Does the heat generated by incandescents help in the winter when you need to heat your home anyway?
What about replacing your perfectly good old electronics and appliances with Energy Star ones? Is that worth the waste generated? Does that depend on the options available for disposing of them? What if you donated them to charity?
We know that locally-grown produce is better than imported produce. But how far is it worth driving to buy it? Is it worth driving to the local supermarket if it means you'll use fewer plastic bags?
Is it worth buying organic produce if it goes bad faster than I can eat all of it, thus requiring me to throw out some every time? Would it make a difference if my building had a composting program?
Is the extra energy required for a trip to the beer store worth it for the benefit of returning your bottles instead of putting them in the recycle box?
Is it worth washing your clothes in cold water if it reduces their lifespan (by making it more difficult for stains to come out)?
Is the energy saved by using the dryer on low temperature worth the energy spent by having it operate longer (because it takes longer to dry on cold)?
I don't know the answers to any of these questions. I don't have the information to calculate any of this. But I really wish someone would. It's one thing to self-righteously say "X is better than Y" when you're talking about only one factor, but real life consists of a multitude of factors. Give us some cost-benefit analysis!
I ask questions like these all the time, and I make up answers for myself, and I have no idea if the answer is factually correct. For example, I don't throw out working incandescents light bulbs and replace them with CFLs, because it seems wrong to throw out something that's still functioning, when it's going to stop working eventually anyway. I keep a supply of CFLs handy, and when the old incandescent burns out, I replace it with a CFL. That seems like common sense to me. But common sense is often not supported by evidence. Some things are counter-intuitive.
Now, several readers are going to pose answers to the questions here, but chances are, they are also intuiting the answers. What we need is a website or other reference that pulls together evidence-based answers to these types of questions - an environmental footprint cost-benefit analysis generator, if you will.