USUALLY harmless doesn't mean ALWAYS harmless. Not to say this particular event is dangerous, but relatively dangerous events resulting from CMEs is not uncommon and happen roughly every 100 years. They haven't been a huge problem before because the world wasn't reliant on technology. CMEs that are large enough can damage electronics and bring down electrical infrastructure. 100 years ago, that was a minor annoyance. Now....having one half of the earth losing its power infrastructure, satellite communications and electronics would be devastation on a massive scale.