I know from firsthand experience, ignoring Digg for the moment, that there are at least 500 million people who use a featurephone in India to check news, cricket scores, horoscopes, make payments, send emails, and send text messages. Their threshold for device frustration is much higher than mine.
I would still question the millions or billions of users who view the web only on their non-smart-phone who will be using social media like Digg.