I don't know about hub scores, since the algorithm is a mystery to me even though I've been around here for three or four years.
As far as traffic, linking to outside sources can affect your PageRank, which in turn may affect your traffic to your page through search engines. Ideally you want to link to sites which are high authority. When you write a hub, linking to a site with a high Page Rank is ideal, provided that the link is relevant to your hub. If it /isn't/ you may actually lose traffic.
Including several links on a page helps to improve the reader's trust in your pages and allows them to find further information, which also providing optimization for your page. Make sure that you use good descriptive anchor text as well, and bear in mind that it's a good deal more important to build backlinks /to/ your pages than it is to link out on your own page. Your best policy is to do both!