Spotify creates oddly balanced shuffle queues when playing from an 800 song playlist, controled from another machine.
To recreate the issue, try this for yourself:
Start by listening to any song, in this example. "Lateralus" by Tool. The playlist is sorted by song. Click shuffle. Open the queue and look at the shuffled songs. You will see that all the queued songs start with the letters I, J,K,or L. None of the songs in your playlist that start with a letter beyond L will ever be in the queue.
Let's try again. The playlist is sorted by artist this time. We will listen to "Lateralus" by Tool once more. Click shuffle. Open the queue and look at the shuffled songs. You will see that all the queued songs are all from artists whose name starts with the letters R,S, or T. No song will ever appear in the queue if the artists name starts with a letter beyond T.
The really interesting part is that this behavior only occures when I try to shuffle from another device. I frequently play from my desktop which has large speakers, and control playback from my laptop. This behavior only occurs when I click shuffle on the laptop, while playing from the desktop. Shuffling songs directly from the desktop works as expected.
Both computers are running windows 7, both running the lastes version of spotify, 220.127.116.11.g8f9312a4.