iTunes 11 is the latest version of Apple's music player and management software, but if you have upgraded your iTunes installation to this latest version you may find that some of the statistics regarding your library are not being updated.
Whenever you play a song in iTunes, the program keeps track of the number of times the song has completed playing, how many times it is skipped, and when these events occurred. This information is stored in the library and used to help determine how to build automatic playlists from the songs you prefer, among other functions.
After upgrading to iTunes 11, however, some users are finding that these statistics are not being updated, and songs can be played numerous times with no change to the dates and counts listed in the library.
This problem has not happened with everyone who has upgraded iTunes, and after users investigated this issue in a rather lengthy Apple Discussion thread, they found that this issue is linked to the use of the iTunes crossfade function. This feature allows for a more seamless transition between songs during playback, which can be useful in some situations; however, it seems this avoids the end of the song and iTunes does not recognize it as having been played.
As a result, if you find that iTunes is not updating play counts, then go to the program's preferences and in the Playback section uncheck the "Crossfade" feature (merely changing its value will not have an effect).
This bug in iTunes will likely be addressed in an upcoming update, but as it stands is a relatively minor issue. While those who wish to keep tabs on their songs and library uses may find this a bit of an inconvenience, it is not one that will have any impact on folks who use iTunes tonight for New Year's celebrations.