The last few months I have seen several ups and downs! The reason being we are ardent fans of magento and therefore we planned to do our corporate site in magento, but we never thought that it will run terribly slow on shared servers, this was a hard lesson for us! We had a drop in page rank and listing in google!
Anyways good sense has prevailed again and we have gone back to the static site we had before! Not all shared servers are as bad as ours was, but you can never tell who is using the resources more on a shared server, so because of another website running on the same shared server your website might perform low!
It is very important for a site to load faster and google considers it very seriously!
We offer magento on dedicated servers, feel free to check our expertize list at: www.enlighteneditdevelopment.com/magento.html
Or for our other services on joomla, prestashop, and wordpress visit : www.enlighteneditdevelopment.com