Regardless of the problems with my implementation, merchants will not enter this marketplace if they have to change their prices daily - and in the current market, daily wouldn't even be often enough! There is no reason that anyone anywhere should pay 1 BTC for a shirt and then twenty minutes later see a price tag of 0.8 BTC and then 1.4 BTC twenty minutes after that. The issue still remains that this market is too volatile for real commerce and if the only people in the market are the speculators, who thrive on volatility, there will likely never be a sufficient decrease in that volatility to make this a worthwhile mechanism for most businesses to transact in.
I see a lot of people reaffirming that I've spotted a problem and telling me that my solution is stupid, wrong or communist but not a lot of people stepping up to do anything themselves. So until someone has a better idea and wants to implement it, stop complaining about my imperfect solution.
I recently started to accept Bitcoin as a merchant, and it was the same day BTC went from 18 to 31 and then dropped off pretty low against the USD due to heavy sales.
So what I did was making the order processing partially automatic; the customer select Bitcoin during checkout in the online shop and gets information how to proceed in the order confirmation email automatically. When we receive an order I browse through the recent currency trade stats/graphs for the past days and reply with an offer via email which is time limited depending on how big the BTC currency fluctuations are against US Dollar. This is also a good way to get experience with BTC, and maybe at a later stage implement fully automatic handling.
In addition to this, in a way to even out the BTC currency losses when customer "gets too good rate", we keep some of the customer payment in BTC (eg. like 50%), and exchange the rest to USD. Since I believe the Bitcoin will increase in value against the USD eventually, even if it takes a month of swinging up and down, half of the customer payment will then increase enough to cover any losses we had at the time of purchase.
To survive as a merchant these days you have to improvise and adapt, this is nothing new for us. I think the people worried mostly about currency fluctuations are miners here in the forum, funny that they seem so concerned about merchants. My advice; when the the rate drops down, stick with your Bitcoins, don't panic. Hasty decisions are rarely good.
I've just updated the site (and API feed) with new code. It now displays the most recent price, a four-hour moving average price and the standard deviation for that same four-hour span. I'm suggesting that merchants list their items at the low end of either the 68% or 95% (1 or 2 standard deviation) brackets since that's the lowest value BTC is likely to swing to before you get a chance to cash out.
For investors, buy when the market is more than 1 SD under average and sell when the market is more than 1 SD above average (use other tools and knowledge obviously, but this is something worthwhile to put in your toolbox).
Similarly, miners should hold coins until value is above the 1 SD range (or above the 2 SD range if you're really patient) to sell.
Finally, the standard deviation itself can be used as a tool to measure market volatility - a high standard deviation indicates a high degree of volatility while a small standard deviation indicates a rather stable market. I'm doing my data-gathering now to determine what a "good" SD (as a percentage of variance from baseline) is for this particular market and I'll be developing an implied volatility algorithm from that in the near future.
Enjoy