"It appears to me that the single biggest factor contributing to Twitter's impressive SEO is the fact
that Twitter profiles/status pages are sub-directories of Twitter.com (i.e. http://twitter.com/searchviews), as opposed to sub-domains (http://searchviews.twitter.com)," Cancino says.
"Whatever SEO benefits Twitter receives is passed to its sub-directories (this is not the case with sub-domains.) In other words, it's Trickle Down Twitternomics."
And that link value is
golden from an SEO standpoint, so Cancino suggests doing some keyword research for your Twitter posts (much as you would for a blog).