I summed the new members of every month, and get these numbers:
Month Total member
Sep-11 43031
Aug-11 40579
Jul-11 36713
Jun-11 31247
May-11 16764
Apr-11 10805
Mar-11 7881
Feb-11 5343
Jan-11 3964
Dec-10 3127
Nov-10 2447
Oct-10 2073
Sep-10 1758
Aug-10 1171
Jul-10 656
Jun-10 286
May-10 231
Apr-10 166
Mar-10 93
Feb-10 53
Jan-10 28
Dec-09 19
Suppose that the total member of this forum represents the user base of bitcoin.
and the total user of bitcoin is 4 times large as in Apr-2011.
If we consider bitcoin as a currency, which is used in trade.
If only 2 persons have bitcoin and accept it, there is only 1 trading opportunity between the bitcoin users. 2*(2-1)/2=1
If n persons have bitcoin and accept it, there are n*(n-1)/2 trading opportunities.
If bitcoin's value is determined as a currency, we can reasonably assume that the "value" of bitoin today must be 16 times as in April-2011.
However, the change in value of the bitcoin does not equal to the change in the exchange rate of the bitocin. There are several issues we should take into considerations.
Positive issues
1. The infrastructure has been improved, the cost to realize the trading opportunities decreased.
2. Some bitcoin users who do not speak english don't register on this forum.
3. the exchange rate back in April might be undervalued.
4. There might be another factor k in the formula, n*(n-1)*k/2, the k reflects how likely two person can do business with each other. We can guess that if people in the same town, the k might be larger than two people which one in USA and one in Russia. For example, you cannot order an Russian pizza at your America home. so as the user base of bitcoin increase, the average k is becoming larger and larger. And when user are all programmers, the k will be smaller than a diversified user base with different type of skills and talents.
5. Some people have even more confidence in bitcoin since the price peak of June, as bitcoin survived so many disasters that some famous poster on Quora have predicted, but the developers still around and the chain is longer than ever. Some people just have an unrealized lost in trading and investing in bitcoin, they like to hold and not to decide whether sell or not until the price bounce back to when they buy it.They hold more bitcoin and the amount of bitcoin in circulation decreases.
Negative issues.
1. New coins coming into circulation at a speed of 7200 BTC every day, which increase the M1 at a speed about 0.1% per day. it's fast.
2. most the bitcoin that is belong to Satoshi and his friends has never been moved since created. Maybe the wallet is lost, maybe they just hold it. So the number of bitcoin that is actually being traded and spend in the bitcoin economy, has been increasing at a faster speed than apparently calculation.
3. The price is dropping so fast, that many people may have lost the confidence and interest in bitcoin, and leave this economy.
4. Some users are always registering new users on this forum. However, since the newbie restriction created, I guess this trend is somehow stopped.
5. the exchange rate back in April might be overvalued.
6. The infrastructure improves and the speed people spend bitcoin is faster, so that we can use the same amount bitcoin to have larger bitcoin economy. So the bitcoin exchange rate may drop.
7. Zhoutong started his bitcoin short service. This is very much like a bitcoin bank lending the bitcoin to the market. Now we have something should be called " monetary multiplier" that is larger than 1. with the same amount of bitcoin minted and the same exchange rate, bitcoin is able to serve a larger bitcoin economy.
Whatever, we may still guess that the exchange rate of bitcoin SHOULD be as SEVERAL times as back in April, when before the major media report show up.