yes, absolutely!
social media channels such blogs and forum posts with keyword-rich content and mentions of your brand/products/services add a great deal of value to seo activities.
by including a blog on one client site we turned less than 50 pages into several hundred and, even though it's early days yet, it's making a huge difference to the search results...
in addition the dissemination of this content on other websites is also generating links in which are definitely helping with their performance on the search engines.