Link Popularity - Page Specific, NOT Site Specific
Many people confuse link popularity as being only the root domains popularity. More and more, internal pages link popularity is becoming the influential factor, not simply your home page. Your root domain can enjoy a great link popularity and Google PageRank, but your site won't reap the entire benefit unless your internal pages have links pointing to them too.
Internal linking contributes highly to your sites total link popularity thus search positioning especially on Google. Getting external links pointing to your internal pages has become a more determining search position factor than before.
Google's Webmaster Tools provides a good estimate of your website's link popularity both to the root and internally. You can see how well your site is externally links as well as interlinked with itself.
Finding places to link into your internal pages can be a challenge. Providing your visitors with information they are looking for and interesting content is a link building strategy itself. By using the correct avenues, internal link popularity is a great way to build search visibility, traffic and overall search positioning.