I've worked at places that had it as part of their environmental/energy-saving policy that you must turn off your computer when you leave. I could often turn on my computer, get a cup of coffee, and finish drinking said cup of coffee, before my computer was in a state where I could get work done.
That's a bit silly. There are a couple of things to consider:
1. ACPI power saving modes draw very little current. As long as your computer is configured to drop to that, it's fine. It will resume within 1-2 seconds as well.
2. There are companies which have software which manage this and power your workstations up before you get in and down after you've left.
