Next time you update the stats, could you also include "megabytes added to the block chain" and/or "percent of total bitcoin transactions"?
Updated, and with the calculations you requested. I don't know why I didn't do it originally, I've been curious myself...
It's actually not as much as I thought.
Only 22% of transactions and transaction bytes are due to SatoshiDice (starting the counters after the first SatoshiDice transaction).