When you have a shared server, your information can be compromised if someone else sharing your server does something that causes the server to ‘crash’. That can be just about anything. Installing a script in the absolutely wrong way or with improper safeguards in place would do it.

Their having a very large spike in visitors on their site(s) could slow everything down enough to affect your visitors getting through to you. The way that the programs and scripts interacting with the other scripts and programs operating throughout the entire server can have adverse effect on all of the sites being housed on that server.

You will have the maximum amount of control over your files and web pages when you are using a dedicated server hosting system. That is of the utmost importance when you have the interactive web sites you need to be using to get your web business moving up to the next level, so think very seriously about where you are right now and about where you want to be in the near future!