Google is obsessed with site speed. That is why the speed of a website relative to another related website is now taken into account by Google’s search ranking algorithm. Google launched this change a few weeks back after rigorous testing. While site speed is a new signal, it doesn’t carry as much weight as the relevance of a page. Currently, fewer than 1% of search queries are affected by the site speed signal in Google’s implementation and the signal for site speed only applies for visitors searching in English on Google.com at this point. That explains why the rankings of some of my websites hosted on a shared server suddenly dropped overnight. 
What does that mean to SEO consultants, webmasters and site owners?
It is time to tell your client to get hosted on a dedicated server with bigger RAM and faster CPU. Forget about shared server or Virtual Private Server (VPS) if SEO is very important to you.
That sounds like a good news for web hosting companies.
See Site Speed.
