I've had a total of one frame lost on CF cards due to an issue with the CF card in 8+ years. (and zero lost frames from SmartMedia, SD cards and other flash form factors.)
As a whole, flash memory is extremely reliable, although it is definitely not perfect. While I think I know of a couple of cases where flash media have failed photographers, I also know of at least one case where a CF card went for a swim in the Merced River (not me, but I saw it), another one got run over by one of those warehouse tractor thingies (that one was me, I dropped it at just the wrong moment) and probably a couple of other problematic situations in which the cards and contents survived.
Far more likely to fail are the pins in the camera (I know of several cases of that) and most commonly, loss of the card itself.
_____ Brian... a bicoastal Nikonian and Team Member
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