Most businesses don’t like to use sub domains because they feel like they give them a disadvantage in many areas, such as having a prefix name before your web-site, being ignored by bots and index spiders in search engines and all in all, it just doesn’t look right. So let’s check our facts on sub-domains.
A sub-domain is substitute or second-level of a domain. A regular domain looks as follows: www.jamesbrown.com . A sub domain looks like this
http://bravenet.jamesbrown.com. Sub-domains do not have www on the front of them. All subs start with "http://subdomain/maindomain.com pattern of identification.
Sub-domains rank efficiently well. Search engine spiders and bots are not prejudiced when it comes to the ranking of sub-domains and regular domains. As long as your site has the right SEO keywords and has been optimized, whether you have a sub-domain or regular domain name doesn’t make a difference at all.
Let’s pretend that you site has a lot of categories in it. If you were to submit to a search engine, you could submit each sub-domain as its own individual category and still get a good ranking. Each sub-domain would be looked at by search engines as a new site with its own index or home page. You may want to try creating sub-folders on the sub-domain to get around this so that search engines can read the folder as one set of site information.
People worry about their sub-domain getting banned if the main domain name is banned. If the main domain is banned, it will have an effect on the sub-domain. You see this happen often in adult content sites that have violated certain agreements that they have signed with a provider that does not want a domain used for adult material.
Again, there is nothing wrong with using a sub-domain. If you want to develop each sub-domain as its own entity, then by all means, do so. If not, get yourself a main domain name and use that as a certified landing page.