One difference between NR and tech: With tech products it's relatively easy for competitors to make the same widgets, and drive prices down (e.g. all things computer-related). With NR, there's only so much of it, and it gets increasingly expensive to find/extract as it gets used up (and the global middle class increases).

Also, in the pre-2000 bubble tech companies without earnings were trading at huge prices. There may be a bubble now in oil for example, but I think most NR companies would have decent earnings even if commodity prices were lower.

At least this is what I tell myself to keep holding PRNEX.