There's a lot of pros & cons - off the top of my head:
Pro: more content means more webmasters promoting the sites
Con: more webmasters promoting the sites can lead to the webmasters not getting listed because of overused content
Pro: it's easier to sell the surfer on the site if you're using hte content from the site
Con: surfers might see the content so much that they think they don't need to join the site
Somewhere inbetween both of those is a happy middle ground
