No way is bing higher than digg, they've got the initial hype thing going, but watch what happens when that dies out.
Fill a turd with enough cash and it will be huge..... Weather enough people will turn that turd into a diamond is another thing.
your comparing oranges and cars IMO pairing a search engine vs a social site? its totally different not even niches, but market shares, its a different share of the Internet maybe trafficwise... but its not really bigger