This is a question I have struggled with and although i cannot prove it I would say yes.
I was making blogs to funnel pr and traffic to my main site. I was using a pyramid link strategy and at the bottom tier (yes they were spammy profile links but hey) I used my target keywords as anchor text all the way up. The result was a continual increase in rankings over time - since I kept blasting links to the bottom layers.
I did SEO for another of my sites the same way and this time used generic text on the bottom layers. It was easier but the progress in ranking was a tenth of the other site - both sites were in the same niche and had good onsite seo etc.
This observation led me to believe that Google uses incoming Anchor text to determine relevancy - perhaps they take the most common incoming link anchor text and tag that webpage with it to help classify it for relevancy. Onsite factors would be more important but I believe Google may use incoming anchor text to tag pages for relevancy.