Alexa's toolbar is IE only and you'd assume Digg has more of a Firefox skew than something as mainstream as C|Net. There is a fair chance Digg passed C|Net a while back, even if you apply the usual caveats to Alexa's data.
Smarter people than me (the two above) ponder this the whole time. The question is now whether there is much benefit in a mashable, platforms-everywhere world, to run a traditional destination/experience site. If the experience is moving to a reader's social network or into their RSS reader or some other space, how should a destination site respond?