The debate about using a non-www prefixed URL versus including the www still rages on in the SEO world, but the key thing is to ensure there is consistency.
This means that if you choose to have the www prefix, then you'll want to ensure all URL calls are to this pattern. Especially since there are SEO implications involved with any URL change, attention to detail is critical here. For this recipe, we'll redirect all non-www to www-based calls, but the reverse is simply a matter of slightly modifying the rewrite rule.
