This is a question I’m asking myself all the time, but my feeling is that technology does far more good than bad in the long run.
Let’s take cellphones and computers as examples: Both provide a means for communication, which reduces paper waste, decreases travel (for visiting people and for transporting letters), and speeds up progress (research, discoveries, and information can travel and spread more quickly, thereby improving everything else).
Also, both provide access to knowledge, which is very important and, I believe, should be basic a human right. Access to knowledge improves societies and provides the tools necessary for our species to evolve in a more sustainable direction.
Can the Earth support 7 billion mobile phones? Well, we’ve already got around 5 billion and the infrastructure to support that, so I’d say yes. However, I think we need to change the way we look at materials and longevity. Computers and mobile phones shouldn’t be replaced every year or two… they should last at least a decade or more.
Things like solar power and provide a clean, practically unlimited source of power. What needs to change is our mentality around these things.
As I mentioned in my first comment at the top, the shelf-life needs to change and each of us can start by maximizing the longevity and usefulness of the technology we keep with us. I have very little paper waste because I do nearly everything digitally. I refuse to buy paper books when digital versions are available — who cares if digital is less comfortable to read: it’s a sacrifice I’m willing to make.