This is Apple pulling a James Bond on record companies. In a letter addressing record labels, Apple states, "We are pleased to let you know that we are preparing to increase the length of music previews from 30 seconds to 90 seconds on the iTunes Store in the United States. We believe that giving potential customers more time to listen to your music will lead to more purchases." So previews of songs are now 90 seconds. Which is awesome because often previews often cut off before they get to the meat of the song.
My favourite line in the letter is, "All you have to do is continue making your content available on the iTunes Store". This will only work for songs that are two and a half minutes or longer. There are many songs out there that are a minute and a half and even less (for example, "Judy Is A Punk" by The Ramones). Previews for these songs will still be 30 seconds. Just so record companies don't choke all over their shock.