How Effective are Mutiple Domain Names?

I have written, in the past, about the advantage of alternate domain names for your business and their effectiveness in increasing your traffic and search engine rankings (http://www.sharpwit.com/newsonline.html). However there are some qualifiers to look at while using alternate domain names

1) Although alternate Domain names may increase the number of visitors to the initial page they will not enhance the visitors to other parts / sections of the main site. 2) In order to improve visit numbers on the "back pages" of the site use navigation bars and text links to the "other pages" 3) It is advantageous to utilize the differing content of each page as a tool to obtain a larger audience. 4) Each alternate Domain name can use different key words and phrases as well as different text which is specific to the group of visitors you wish to attract.

Bruce Clay , of Search Engine Optimization fame, states "multiple URL's pointing to the 'same page' .... will not be simultaneously indexed by multiples of the URL's". If alternate domain names all point to an identical 'page of the main site' they will not significantly improve the 'main site's search engine position'. Mr. Clay continues to say "Worse yet, the URL (address of the alternate domain name) that does index that page is not going to necessarily be the URL (the address of the main web site) indexing the page links from that page to the rest of your site"

"This 'same page' rule may not apply" if "the URL's, page content would be unique throughout the site, thus recognizing the pages as being the same may not happen". Thus by utilizing "links" to other pages/sections of the main web site you can minimize the risk that the main site's favorable rankings would be jeopardized, but would instead, be enhanced.