I'm wondering what the implications are for having multiple domains for different service areas of a company? I realize having multiple domains for one company can be troublesome because of the possibility of duplicate content, keyword cannibalization, and linkbuilding to multiple domains. But when the domains are for very different service offerings/unique business functions that each serve  their own purpose (and have  different positionings), is there a downside to having more than one domain? Any thoughts would be appreciated!

Today I met with a firm called Localeze that provides local directory submissions.  I understand the importance of this service if your site is competing locally, however I'm not sure the effects of local SEO for a national brand. Our firm gets most of our traffic from across the country, not just one location, and our business is scattered (which is a good thing).  We rank for service related keywords that are not tied to a location. We do not show up for local results so our business in our immediate location is weak.  We would like to increase our local presence in search engines but I want to make sure that this will not take away from our national presence. Will optimizing a site for local search negatively affect general rankings? Thanks