There's clear demand from searchers who increasingly expect user reviews as part of their local search experience. Social and local search are on a clear path towards merging.
Search algorithms & popularity factors: link, social, click, blog, industry. Since modern search engines are concerned with popularity and not direct relevancy, & big firms up the price of text link buying beyond affordability...
Great wideranging riff on analytics and nonprofit evaluation of methods: how do we know that blogging is good for our oragnization? -> how do we increase our traffic?