I just saw that the Danish have released AIS data publicly. I was excited until I saw what one of the files looks like. It's not RAW AIS NMEA data. That means it's crap for anyone wanting to do use it for rigorous research into AIS. You don't get to see the station info, the comm state, or any of the interesting channel messages. You won't get to see each of the ship name messages. Or the meteorology/hydrology messages. You also won't be able to do anything if you find they have a processing bug or don't like the way they choose to conflate msgs 1-3 with 5. Also, what exactly is the license / copyright status for the data? Big bummer.
That's in addition to the already annoying marine link story that doesn't actually link to the data. http://www.marinelink.com/news/available-denmark-makes423497 MarineLink does an amazing job of annoying me.
And they named the files MMMYYYY so they don't sort nicely on their ftp server (wait, ftp? what year is this?) Extra bonus of using a zip so I can't zcat/bzcat/xzcat a partial download to see what I'm getting into. At least the most recent data is available by day as an uncompressed file.