Here is Wenner on the change:
The large format was one of Rolling Stone's trademarks — and it became a physical reminder of our roots in San Francisco and of a vital time in our cultural history. That's a lot of history, and it is not without a wistful feeling of sweet memories of those days that we make this change.
It was not a decision we made lightly. We felt this was the right move but remained a little uncertain, knowing this was not just up to us but also in the hands of the large number of passionate and longtime Rolling Stone readers (there are nearly 13 million of you, when you count the number of people who share their copy).
Thus, a few months ago, while putting together our annual summer double issue, we produced a version of that edition in the size and style of the one you now hold and mailed it to 3,000 subscribers to get their thoughts. The response was a major surprise: Readers loved it. We realized that the only reason to resist change was nostalgia.