The documentation for QThread was written when it was abstract and subclassing was necessary. However, in Qt 4.4, it got a default implementation of run() which spins an event loop. Subclassing QThread is no longer necessary, and we don't even recommend this.

See Brad's blog for more details:

http://blog.qt.digia.com/2010/06/17/youre-doing-it-wrong/

As he points out in the comments, the documentation needs to be updated to describe the recommended way of using QThread.