I'm in the process of creating a website with number of microsites as subdomain. Can someone advice me if says 6 months later, I want to switch to another host and thus, a new IP, will it affect the SE ranking I manage to chalk up up till that point of time? In the same context, how will this affect people who upgrade their server from shared hoting to says, VPS or Dedicated hosting? If it doesn't really affect, then why do some people advocate having an unique class c ip for SEO? Thanks for any advice.