The transaction displays "Coin days destroyed", which is an indication of past transaction activity. When you haven't spent 20 BTC for a day and 5 BTC for a week, there are 20 * 1 + 5 * 7 = 55 coin days destroyed. This particular transaction has 143,132,916 (!) coin days destroyed; at least some of 180,000 BTC spent today haven't been spent for past 143,132,916 / 180,000 ~= 795 days, just over two years, as per the pigeonhole principle.
I clicked on the question mark next to bitcoin days destroyed, which explained a bit more about why his is interesting other than the volume -- looks like these are coins that haven't been touched in a couple years.
I was thinking it's perhaps promo for blockr.io ? But, it is interesting because it's a transfer of coin worth over 110 million dollars USD (with today's conversion rate anyway).
I would love to know what this is that we are looking at, that means nothing to me, but still make it to first page of HN.