https://blockchain.info/charts/estimated-transaction-volume?...
I used the log scale to make the point that transaction volume is relatively slow-moving on a log scale. That is certainly not the case for the exchange rate!:
https://blockchain.info/charts/market-price?showDataPoints=f...
Incidentally, the volume graph has a notable spike in December 2011. I've Googled and asked around a bit, but don't have a good understanding of what caused the spike.