While comparing with a competitor's site, I used the Opensitedirectory backlink thing. To my shock they had 815 backlinks inbound to their site. After filting it though, they only have 18 links from other web site domains. The other 790+ links were backlinks from their own web site and their blog and PR Newswire writeups that they did themselves.
In any case, do backlinks from your own domain name to your index page give you any ranking benefit at all?