You’ve probably heard a lot of expressions that describe this phenomenon. Phrases like “in the wrong place at the wrong time”, “guilt by association” and “judged by the company you keep” refer to a real life problem that occurs when people around you cause fall into trouble.
How does this at all related to web hosting? If you use shared hosting (name based virtual hosting), your website may very well end up being judged by the actions of those who share the server with you.
The first problem you may face is that your hosting account to share an IP address with more than one account to another. This means that your domain can share the same IP, as a place called “FreeiPadsForAll.tld”. If this place does not do something wrong, like spam, you can find their place in a black list where it belongs.
The second problem is of all shares. Some users have much more than their fair share. These people should be using a VPS or a dedicated server, but instead, try to save money while grabbing all the CPU cycles and memory, bogging down the server.
An obvious solution is to choose a dedicated server, but if your site is small, which may be an exaggeration. Also very expensive for a person with only basic shelter needs.