Link Popularity is something Google is very concerned with. Getting all important links back to your website from other industry similar sites is a key indgredient in the recipe of Search engine success. Your PR (page rank) increases the more popular your website is and the more links achoring back to your keyword rich web pages the higher position you will have in Google.
Blogging on sites with a similar market to your own is a great idea to start building your link popularity. Whether for the viral marketing potential that can be reached or the keyword specific links backs to your own site blog sites are a ticket to a wealth of exposure.