That's one approach to linking, but there are others:
1) LITTLE OR NO EXTERNAL LINKING. Corporate sites (including many large media sites) often take this approach, not to preserve pagerank but because (a) they don't want visitors leaving their sites, or (b) they're recycling content from printed media and are too lazy to add hot links.
2) LINKING DICTATED BY EDITORIAL CONSIDERATIONS. This is the approach that I use, probably because my editorial background leads me to believe that focusing on the needs and desires of readers is critical to the success of a "content site."
IMHO, linking to other Web sites isn't just an act of altruism--it's likely to pay off over the long run for several reasons:
- It makes your site more useful to readers, so they'll be more likely to return.
- It establishes your site as a "hub" or "authority," and that should result in more inbound links from quality sites (including directories) that haven't asked for reciprocal links.
- If links are annotated and there are enough of them, you'll end up with more pages on your site. More pages = more chances to be found in the search engines.