"Market capitalization" over time Is there a convenient data source and/or graph that gives the "market capitalization" over time for Bitcoin (i.e. the number of bitcoins issued to date times their current value on the big exchanges).

Note e.g. some publicity and attention to this issue due to the xkcd infographic on Money:


Money - XKCD
Zoom in to the part about bitcoin or see the original version:




Note that the date indicated there for the peak so far (July 2011) is wrong, since that peak was on June 8 or 9.  It would be fun to provide some more accurate and precise numbers, though of course there is no one canonical exchange rate and some sort of weighted price may be more useful than the very highest trade recorded.  See some nearby data at:
 bitcoin charts 2011-06-08..11

Update: A closer look at the minute-by-minute data suggests that the peak was at     2011-06-08T17:10  when the mtgox USD price was $31.91.  At that point the most recent block was  http://blockexplorer.com/b/129412 at 2011-06-08 16:56:29 (assuming both services are using the same timezone? UTC?).  That implies $206,476,846 I think: 31.91 $/BTC * 129412 blocks * 50 BTC/block

See also the nice new Bitcoin Pie site that compares market cap for various bitcoin-related currencies (and see Is there an easy way to check out the market cap of the alternative currencies? - Bitcoin - Stack Exchange).
http://blockchain.info/charts/market-cap. 24 hour Weighted price from mt.gox and tradehill.