Bad Shared Hosting Neighborhood

Its true and it can happen. Generally in Shared accounts provided by Hosting provider, all the accounts setup on a particular server share the IP of the server. So even if a single domain of any user hosts a abuse content or anything illegal, his IP will be blacklisted and this will have a adverse effect on other domains as well. But I think the hosting provider is also well aware of such issue and he already takes necessary measures to avoid this.