It would be interesting to compare BtC not only to the USD, but also to a bag of currencies, to see if it relates to a USD devaluation 'compared to the rest' (usually JPY, EUR, GBP)
I guess that, according to the efficient market hypothesis[1], you can expect the price of bitcoins in other currencies to be the same as the price in dollars adjusted by that currency exchange rate. Otherwise easy profit would be possible through arbitrage, and after some people took advantage of the price difference to make some money the prices would stabilize
at a point where profitable arbitrage would not be possible anymore.
" according to the efficient market hypothesis[1], you can expect the price of bitcoins in other currencies to be the same as the price in dollars adjusted by that currency exchange rate"
You're right, apart from market inefficiencies that's right.
But I'm proposing something else, to analyse the variation (which, of course, for BtcGBP is effectively BtcUSD * USDGBP) against other currencies to see if it's (for example, in this case the price of BTCUSD rising) if it's a dollar devaluation or if it's BTC that's increasing in value
LOL, how interesting? It has been going up related to everything else, even gold & silver. I doubt that there exists a better-performing non-hedged asset.
[1] http://en.wikipedia.org/wiki/Efficient-market_hypothesis