

Yes of course that kind of fraud is serious. If it can be shown that Tesla is screwing with odometers in this case, they will immediately face a massive class action lawsuit from current and former owners, and their stock will tank even more.
It affects routine maintenance, warranties, resale value, business taxes (based on the current value), and all sorts of other things. I think there is potential for other interesting legal issues, too. If Tesla is lying to the customers, then the customers are reporting false data to their insurance companies and state regulatory agencies. So there could be legal issues connecting to those groups as well.
Warranty. Read the article.