I've looked for (and cant find) a graph that shows how much BTC is flowing from point to point. since all transactions are public this data could be gathered by analyzing each block and taking a sum total of amounts moved.
http://www.bitcoinmania.com has transaction counts, and
http://earney.homedns.org/cgi-bin/page.py?type=spent has transaction volume
But consider situations like this: Each time 0.05 is spent from the Bitcoin Faucet, http://freebitcoins.appspot.com there currently is about a 250 BTC "change transaction" created for each. i.e., "volume" is exaggerated 5,000 times versus the actual transaction size.
I don't know the best ways to adjust for these. Possibly:
- If there is only one "output:" amount, then it is safe to say the entire amount was transferred.
- If there are two "output:" amounts, then it is safe to say that at least the smallest "to:" amount was transferred.
- If there is more than one "input" amount, then it is safe to say that all amounts except for the smallest "input:" amount was transferred. (this needs verification)
Keep in mind, I can also send bitcoins back and forth between two of my own wallets at no charge. Thus the "total volume" can be manipulated easily -- i.e., Transaction volumes alone won't tell the true value of Bitcoin and any attempt to give merit to using this metric as a significant component of an investment decision will likely cause pain to the investor.
That's why I think such graph is useless. 