I think it depends on what your aim is for your hub or website. If it's just for information then a small number of hits may satisfy you. If you want to make an extra income using Adsense then you are probably looking at working towards 5,000 + hits a day. To make a full time living then you'll want even more hits.
Then again, it's not all about hits. Are your readers looking to purchase a product? If they are then you could have a lot less hits but more buyers. In this case having targeted traffic is better.