That's a hell lot of blocks to only have 1 transaction. And I wouldn't even call it one transaction, I would call it ZERO transactions!
I knew this was possible but I didn't know the number would be this high.
A lot of these are pretty old. In the early network there were very few transactions.
There is a balancing act though for miners, especially any with low bandwidth, because losing an orphan race as a result of transmitting a large block is much more expensive than mining transaction fees (over 200:1). Very few miners (more correctly, pool operators as they select the transactions) allow maximum-sized blocks though; most have run with a limit. I posted an analysis last night in another thread (
http://hashingit.com/analysis/39-the-myth-of-the-megabyte-bitcoin-block)