Oprah Winfrey enthused about the Amazon Kindle on her show today — it's her "new favorite thing" — and had Jeff Bezos on to announce a $50-off offer good till Nov. 1. A plug on Oprah is ordinarily a sign that a product has crossed over into the mainstream. But her show's audience has been slipping lately, and it's unclear how many cash-strapped citizens will be willing to part with $309 (after the special offer) for a new techno-gadget, for which they then have to shell out more money for DRM-encrusted content.