"Serious as in screws with your service, screws with other customer's service, or as in damages equipment?"
Cable systems are designed to be a closed system no ingress or egress. This ingress that you are seeing is most likely causing many problems in your neigborhood "NODE". Ingress or noise will cause data loss or corruption resulting in slow data speeds, intermittent modem connections, VOIP problems such a jitter and echo, and digital video problems such as pixalation and black screens.
These problems are caused by damaged cables ffrom such things as animal chews, cracked cables from storm damage. But the majority of issues are caused by poor conectors and cable that doesn't meet the shielding characteristics required by a HFC network ie. 75 Ohms of impedence. This is most often a result of DYI using materials designed for an OTA antenna install.