There is a lot of confusion regarding the effects of using Multiple Domains/Subdomains/Folders on various factors affecting SEO. This situation generally arise when a websites is served in more than one language or when a website have diversified categories.
Following is the list of factors affected by using these 3 different approaches:
1. Geographical targeting (GEO Targeting)
2. Authority/Trust/Domain Strength
3. Sitelinks
4. Control over the website
5. Design & Web Structure
6.Link building and Link structure
To see the detailed explaination have a look at the original content at:
http://www.webseoanalytics.com/blog/multiple-domains-vs-subdomains-vs-folders-in-seo/
