How would a subdomain separated word compare to a full word in terms of SEO? For instance, say that the site del.icio.us never existed, and the site delicious.com never existed. They both were released on the same day. Just in terms of the domain name (forgetting everything else involved in SEO), are they equal?
No they are not equal as the keywords are not the same. You probably need to read about a trick when choosing a subdomain name and it includes using Google's Did you mean? feature.
Wouldn't google read right through the periods and see the entire word, though? For instance, del.icio.us = delicious