I built a digg-like clone at fantasybookmark.com. Google crawled the site, but only indexed about 21 pages out of the 2,000 or so (and growing) pages on the site. We use rss feeds to find and generate content and allow users to comment.
What are reasons we are not getting indexed? Are there ways to solve this?
Your site appears to be quite new and full of low-quality content. For 90% of the pages, the only unique content is a title and one-line description. It may have been better to start with a small group of hand-picked articles on which to generate discussion and build a community.
A brand new site with thousands of pages can sometimes ring alarm bells with Googlebot. There have been cases of sites generating masses of unoriginal content and managing to get ranked for obscure long tail keywords even though the site is full of spam essentially.
All the usual advice will apply here: create an XML sitemap, check your site in Google Webmaster Tools. You could also try increasing your crawl rate in GWT.
