But this doesn't even seem like laziness or carelessness - if you dropped your rag on the floor and then wiped the table, I get that. But to take an object solely designed to clean a floor and then use it in on an eating surface? I just can't fathom

I equate that with cooks or waitstaff spitting in someone's food. It is deliberate. And I find it interesting that the article stated, "Disney officials said...she is no longer welcome on Disney property." That seems a bit drastic for someone who was just a disgruntled employee/contractor.
Regardless, this just reinforces my policy of bringing disinfectant wipes to wipe our tables down! I'll just make sure I do it for the food courts too!