my blog is 6 months old, with frequently updated content. Yet, not a single page is indexed by Google. Why is that so? isn't wordpress set up for SEO by default?
I have to ask the obvious here; have you changed your privacy settings to allow the blog to be accessible by search engines. Blogs in general and WordPress blogs are typically well crawled by Google and the other search engines. If you have already made the blog visible, you may want to create a sitemap and submit it to the search engines. You can use the plugin Google XML Sitemap to create the sitemap with almost no configuration. The plugin is available here http://wordpress.org/extend/plugins/google-sitemap-generator/. Hope this helps.
Check under Settings/Privacy. Is the site marked as private by accident? It's happened to me. I'd also suggest installing the Google XML sitemaps plugin which will update your sitemap as well as ping relevant services when content is updated.
It's probably also worth checking your robots.txt file to see if you're excluding the whole site for some reason.