Linux-hero wrote about how Ubuntu kills your hard drive. The situation is somewhat less clear than you might think from the article, but the basic takeaway message is that Ubuntu doesn't touch your hard drive power management settings by default. In almost all cases, it's more likely to be your BIOS or the firmware on your hard drive.
The script that's executed when you plug or unplug your laptop is /etc/acpi/power.sh. The relevant sections are: