Medication Errors and Write-ups

I have several friends at work who have had "write ups" for medication errors (1 was major...giving too much insulin and one of the others was forgetting to administer a Vitamin). At my facility, if you get 3 write ups you are fired!

I can understand the insulin error, but we are all human and make mistakes, especially when we are understaffed as we so often are. I would better understand an incident report being filled out for a medication error, especially if it wasn't a serious error...but to be written up over a multivitamin? I'm not going to mention the other errors but these nurses have come forward to our supervisors as they should do, called the doctor, and received a write-up the next day.

Is this standard? Just curious.