|A better gauge of a Web entity’s user profile would be to look at the composition of PVs, because heavy users will drive PVs and tend to counteract the diluting impact on the core target that a UV metric can have. In December 2007, for example, Media Metrix reported that 62% of Unique Visitors to aarp.org were age 50+ (eligibility for AARP kicking in at age 50); but 77% of their Page Views were accounted for by persons 50+, and 79% of their total minutes.
But there is another important reason to think in terms of pages when assessing a web entity’s audience make-up. Ads are distributed across pages, not UVs. The more pages one consumes, the more ads one is exposed to, and the more likely that consumer is to see your ad. If an advertiser runs a campaign on a site, the audience profile of the exposures to that campaign will tend to mirror the profile of the Page Views, not the Unique Visitors. In the AARP example above, then, let’s restate thusly: 62% of the aarp.com unique audience is comprised of persons 50+, but these persons see almost 80% of the ads.
Josh Chasin, Where The Buys Are: Ads Live On Pages
Something else I want to remember that Tris Hussey wrote: Don’t look at a link away from your blog/web site as asking people to leave, think of it as building a larger network of people who will link to you.