Here's an interesting research study by Junghoo Cho and Sourashis Roy at UCLA, which found that popular sites get more link partners than new sites by virtue of their high search engine rankings. If a site is popular then everyone knows about it and it gets more link partners. If a site is unknown nobody knows to link to it.
A personal example (and yes using a personal example is a fallacy of thinking): remember the new site SEO I wrote about regarding my father's Collectible Car Show Photos? A search on Google or Yahoo for link:http://www.nashnut.com shows no results. Alltheweb shows two backlinks, both from pages on www.nashnut.com. Now it does have a few links; I got it into a few free directories and linked to it from this blog once before but you see the point - it isn't accumulating links because my father hasn't done any linkbuilding.
Now I haven't done any linkbuilding for my ESL site in the last few months. But I have hundreds of emails that I need to respond to one of these days about link exchanges. I get more every day. I am in the enviable position of getting way too many link exchange requests. I have finally set up a directory (which I wrote about yesterday) to make things more manageable. Now I reply to people and tell them to submit to the directory. For some reason most don't, probably because it's not showing PR yet.
Anyway, I digress. The point is that popular sites get lots of linkbuilding opportunities. New sites don't. That means that new sites will have to work pretty hard to attract link partners. It's also bad for the web. New sites might have good content but they still won't get links unless someone does a lot of work. And if they don't get links they won't do well in the search engines and no one will see this great content.
Although I should point out that even with just a handful of links nashnut.com is getting about 60 uniques a day, and some from Google and Yahoo for weird search terms like "1933 Auburn Car".
Trade links with seo-search-engine-ranking.com
http://www.seo-search-engine-ranking.com/ad_network_222.php