A practical outcome of the bound (that the PageRank change for a new link is bounded by the PageRank of the source of the link) was the WordPress link selling affair from a few years ago.
Every WP blog had a link at the bottom: "Proudly powered by WordPress" - which meant there were lots of in-links to WordPress's main site. Links from WordPress were therefore very influential, and the WP admins sold links to SEO shops for a tidy sum. There was some outcry when this was discovered, as I recall.
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A practical outcome of the bound (that the PageRank change for a new link is bounded by the PageRank of the source of the link) was the WordPress link selling affair from a few years ago.
Every WP blog had a link at the bottom: "Proudly powered by WordPress" - which meant there were lots of in-links to WordPress's main site. Links from WordPress were therefore very influential, and the WP admins sold links to SEO shops for a tidy sum. There was some outcry when this was discovered, as I recall.