One thing I keep reading is that the social media sites are a good way to ensure that your blog or website gets indexed by the search engines quickly. I just had a good illustration of that.
Yesterday I discovered that one of the pages of one of my sites wasn't yet indexed by Google. I don't know why that was, because all the other ones were.
Anyway, last night I included the URL of that particular page in a tweet. Sure enough it's now there in Google's list of pages for that site.