I was about a year into working for this small marketing company as the only developer. I was still pretty new to development, my first real gig, 2006'ish.

Form processing was still a struggle for me, so my really cool idea was to use an open sourced tool that would create and process any type of contact form, (think wufoo, but on your own server)

Anyway it was working great, then a few months later we decided to move all 30 of or our small clients to a new server, I moved everything over and deleted the old site (didn't make a backup of any DB (who does that?) got a call the next morning that none of our contact forms were working and nobody had any info stored from previous contacts.

Spent the next 2 weeks getting really good at php. We never did that again.