I agree with Pimpsy. We're like a little isolated speck. There are millions of planets a whole lot bigger than us - some with resources that could actually be used. We are already wasting all our resources, so, if there were 'high tech' beings that had been amongst us for years, it would be far more logical for them to go all hulk on us before we developed this far.

The only thing Earth can offer now is extra space and seven billion slaves. Oh, and water, if the aliens like to swim in what is more or less now polluted muck.