Fixing toilets.
In my early years, we had a small team that worked alone in a DC we had a large presence in. Support, hands and eyes, installations, basically anything and everything required to keep the services going.
It was then decided by the Office Manager of the local London office (a few miles away) that we could carry out general office maintenance tasks for them, because after all if you have IT training you must also be a qualified electrician and plumber...
One day we had a request from her to repair one of their toilets. I told her politely to ring a plumber, which compelled her to write an email to my manager and hers about how "unhelpful" I was. I never went over there again.
Biting the hand that feeds IT
