Add-on Domains + SEO?

[1234567890]

I have a main website, and three other domains set as an add-on domain. Essentially their files are in a folder in the main domain.

Is this bad for SEO and how Google will index my site?

[seo_promotion]

Read this interesting article on whether you should go ahead with main domain or subdomain when it comes to search engine optimization.

Search engine optimization : Subdomains/SubFolders (http://www.seohawk.com/blog/subfolders-vs-subdomains-seo-analysis/)

[felgall]

As long as you don't link into the folders from your main domain it will not make any difference.

With shared hosting there are typically dozens if not hundreds of different domains in different folders on the server.