I just watched the WebProNews interview with Vanessa Fox (via TheBuzzBox), where Rand Fishkin asked Vanessa about Sitemaps. Basically, Dave Naylor said sitemaps is for SEO sissies, and Rand wanted to know if Dave is right (or something like that).
Vanessa seemed to agree with Dave Naylor: you don’t need to use sitemaps if your ok getting your site spidered. There may be additional benefits to using sitemaps, and there may be some convenience brought by sitemaps, but (by my read) Vanessa didn’t offer any compelling reasons why a healthy site needs sitemaps. But Vanessa did clarify that it has nothing to do with rank, and whatever additional benefits there may be, they have nothing to do with rank.
Why does this matter? It doesn’t. Unless it does. It doesn’t matter if you don’t have any concerns. You use Google accounts, use sitemaps, enjoy the webmaster tools Google provides, whatever. But remember you cannot revoke a claim on a web site. Once claimed (via sitemaps), the site is “owned” and Google Trust is granted. Can it be ungranted? Can ownership be revoked? What Google does with information is up to Google. Every bit you provide is another bit that will be used outside of your view. Forever. If you’re okay with that, then you have no worries.