Right, but why so many at a time? Also it cannot be the same coins two times, because they would have to sit for another year before scoring again in the chart.
If you have an address that has 1000 coins, the default client never just moves one of them and leaves the rest where they were. Normally, it moves all
of them, sending one where you want it to go, and the other 999 to a new address.
So this doesn't mean that many coins are being spent, necessarily - just that they're being spent from a heavy purse.