Yes. There is a limit to how much content a web server can serve each second. A single website may experience such high traffic levels that it begins to experience delays in processing queries. With shared hosting, there may be hundreds of websites, all of which would add to the web server's load. There could be a severe issue for all of them if more than a few of them become really well-liked. Memory and processors both run the risk of doing the same thing. Numerous websites depend on calls to a database and interpreted languages like PHP. These demand processing time and memory, and if there are too many of them, they can all suffer. Processing and memory may be more vulnerable to issues than the web server because slow database queries and poorly developed apps can affect even low-traffic websites.