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I don't have any insight into this, but am interested what people in the know think...

Google not indexing Yahoo Directory listings makes 100% sense to me - they don't like taking signals from paid links, Yahoo directory is one of the biggest paid-only link directories. It wouldn't take many manual reviews for Google to entirely devalue every Yahoo Directory listing.

Also, I don't think you should be worrying about your PR all that much - part of the reason it's updated so infrequently is because the big G doesn't want webmasters to obsess over their pageranks... SERP rankings however, are updated as often as they need to be, and so are a far better measure of your SEO success.

We focus our article link building on non-networked sites / blogs. The reason being that there are loads of very-spammy articles already on most sites that are part of such networks, and they tend to need a monthly fee.

Contacting bloggers / journos directly takes a lot longer than a submission to spinning/posting service, but tends to be a) free, b) high(er) quality, and c) the articles stay online as long as the site does. We tend to find sites/pitch articles inhouse, then outsource the actual writing to freelancers for £10-15 per hit.

Some great resources for finding blogs/journos that are open to guest bloggers:

• www.bloggerlinkup.com

• Watch #journorequest

• Use the twitter tool to find blogs using a keyword who have recently posted about other guestposts they've had - https://docs.google.com/spreadsheet/ccc?key=0AvrsfAmTCtRudFRnMFE5RTlGZ0RzNkdzT3NreEFwd2c