They say:

There is an opt-out available for this feature. Free accounts opting-out of using the Air style for mobile devices will still be able to view their own journal in their selected style. Paid & Permanent accounts opting-out of using the Air style for mobile devices will also allow others viewing their journal on mobile devices to see their journal in their selected style. This settings is available on the Display section of the Settings page, and is listed as "Mobile View."

Go here: http://www.livejournal.com/manage/settings/?cat=display