Blood glucose over 180 freaks me out, which is why I have an A1C of 5.1. 350+ IS a big thing and ketones ARE a big thing and need to be corrected. Running high like that for any extended period can put you in the ER, and fast. Look at some of the posts here about their experiences with high ketones and what happened.
That said, I also agree that a high once in a while should not be a complete freak out. Personally, I prefer a low, because I can treat it quickly and go on. High BGs take time and sometimes even days, if the conditions are correct (illness, stress, etc.)
I always try to figure out what happened (hi and low) so I can avoid the situation the next time. Experience is a great teacher.