If you run only Google adsense how much traffic you need to earn $100 a day? This is not my question but everyone’s who is not earning 100 dollars a day. There can be endless discussion on this topic, one will say you need a large traffic base like TechCrucnh or Mashable, another will say you should be on a niche. One will say a good web design can earn you $100 a day because traffic can not measure of your earnings. another will say you should use high paying keywords in your posts.
If I will say about my blog I am too far from $100 per day. I can say if I get daily 20k page views I will earn $100 per day but at this time I am nearly 2k.
A targeted traffic can earn you more, you can experience it if you will be ever featured on content sharing sites like Digg.