I was ashamed of my naivety when I worked on an freelancer-scheduling app for event planning.
I was embedded with this team of about 15 people whose job it was to fill slots for servers, greeters, busboys, drivers, etc for a large event planning business. I sat with these people for 2 months, learning how they did their job and writing some software to help automate it.
When I got done they fired all but 2 of the people because they weren't needed. I really didn't see that coming and felt terrible, especially since they had really helped me succeed at my job.