While most developers think about optimizing their Facebook viral channels, most don’t think about SEO as an important user acquisition strategy in the same way that most webmasters traditionally do.
To help app developers increase their prominence in search engine results pages (SERPs), Facebook recently enabled developers to serve XML sitemaps off the apps.facebook.com. Sitemaps are used by webmasters to notify search engines of updates to pages and page structure, and generally are a worthwhile exercise in any SEO strategy. Since apps are served from apps.facebook.com, developers get to ride on the back of Facebook’s PageRank – potentially a big leg up on regular web apps.
Obviously, applications that serve pages without requiring logins have the most to gain from SEO, since Google’s crawlers don’t login to Facebook and install apps.