A couple of months ago, a group of astronomers asked us to run a workshop at Caltech in conjunction with their annual get-together: they'd cover travel costs for two instructors, and seats at the workshop would be reserved for them. Which would have been fine, except when I pushed the button to create the workshop, I also created an EventBrite signup page and a Software Carpentry bootcamp page with open enrollment. As a result, I had to send email to 15 people last night to say that there isn't actually room.
I'm very sorry for my mistake, particularly as some would-be participants moved other commitments so that they could attend. I'll try to arrange another workshop in the area as quickly as possible, and put everyone who was bumped at the front of the line for it. I'll also try to put some safety checks into my workshop setup process (or better yet, not try to set things up at 11:00 pm after a long day at work).