If you have a WordPress 3.01 Multisite installed with several sites likes blogname.mydomain.com and you make domain mapping so that the site is accessible at blogname.com or differentname.com does it have any effect to SEO? Do good domains improve the SEO and therefore it would be good to do domain mapping? What if you don't do domain mapping, but redirecting a domain like differentdomain.com to blogname.mydomain.com? I think, since WordPress 3.0 has the multisite feature, domain mapping will be more common than ever before and therefore in regards to SEO my question is really important as domainnames that can be good for SEO will be lesser than ever before.
If your options are to choose between say. 1 dothisonline.org, which theoretically is not indexed and has no age or 2. dothisonline.blogspots.com... The dothisonline.blogspot will have many algorythmic advantages based on some authority/age attributes of the serp algorithms. another expample would be dothisonline.typepad or dothisonline.wordpress or whatever. a new domain, newly indexed, and on an unknown ip is way behind for a while. Particularly for very competitive type search words at least.