You might be thinking of Ripple. It is not centralized though.

It took us decades to fully realize the danger of radioactive materials, it might take decades to fully understand the implications of GM. Until we have a reasonable comprehension of the dangers and risks, we should use other methods for improving crop yields

1) Decades? German physicist Wilhelm Konrad Roentgen announced his discovery of X-rays in 1896. Less then a year later Elihu Thomson found that X-rays harm living tissue. 4 years after the discovery of X-rays, it was widely accepted that exposure needed to be limited.

2) I'm not convinced that it ever makes sense to be afraid of "unknown unknowns" without having a threat model. Don't we have to be afraid of everything in that case?

For example, it wouldn't make sense to say this: "It might take decades to fully understand the implications of reading slashdot every day. Until we have a reasonable comprehension of the dangers and risks, we should use other methods for getting our tech news."

It would work better to say something like "Reading slashdot every day is detrimental to productivity, because the time spent reading and posting would otherwise go to useful work." At least then we'd have a minimal model that we can analyze, discuss, test and refine. That way we can also avoid the same problems when we do switch to an alternative. You can't do that if you just cite "unknown risks".

You might want to check out how much copper extraction has grown since 1900. The growth seems modest at 2% per year. But this is equivalent to exponential growth with a doubling time of only 35 years. Or to put it differently, in the space of the last 35 years we have extracted as much copper as there was extracted before in the entire history of human kind. So yeah, maybe we won't run out tomorrow. But real soon now.

But everything thus far shows us that perpetual growth is possible. Technology is a wonderful thing - each year we're able to do more with less.

There are limits to exponential growth. (And make no mistake, growth expressed as a fixed percentage per year is exponential). Technology can push the limits closer to what the laws of physics allow, but technology cannot change the laws of physics.

Let's look at some numbers to drive the point home. Our global energy consumption in 2008 was estimated to be 474 exajoules.

The total energy received by the earth from the sun during a year is about 5 million exajoules, a fraction of which reaches the surface. 5 million is much more than 474. But at a seemingly modest 2% per year growth rate (as it was between 1980 and 2006), our energy consumption will match those 5 million exajoules in less than 500 years!

Think about that: if energy consumption growth continues at the current pace, then in 500 years we'll either be using ALL solar energy received by the earth (leaving none for the biosphere), or we'll have figured out some magic technology to produce 5 million exajoules of energy per year. Assuming the magic technology, where are we going to get rid of all that extra heat? It would effectively be like having a second sun on earth, cooking us in place.

Granted, you did say "do more with less". So lets say energy consumption will stay constant in the future, and instead we'll derive 2% more "value" from the same energy each year. Now you run into a new problem. No matter how you define "value", you run into physical limits. If you define value as "amount of mass lifted out of the earth's gravity field", then the hard efficiency limit is a minimum of 60 megajoules per kg. If you define value as "amount of computation", then again there are limits given by the laws of physics.

Exponential growth is counterintuitive. No matter how far you push the limits (e.g. by colonizing the entire galaxy or inventing game-changing technology), exponential growth will hit its limits much faster than you think. We're talking about growth with a fixed doubling period here.

Finally, I'd argue that we are already experiencing the end of exponential growth today. After decades of growth, in 2004 global oil production reached a plateau. It's not a coincidence that we experienced a major financial crash and recession soon after that. The era of "perpetual growth" is over. The next era will be that of the "zero-sum game" at best.