I recently bought a new iMac (2.4Ghz Intel Core 2 Duo 1GB RAM 20") and I thought that, since it had an Intel Processor and had Bootcamp preinstalled, I'd give a go installing Windows and make it dual boot between the 2 operating systems. (Also, my boss was keen to know whether it would be quicker to use a dual boot system over running Windows in Parallels).
Bootcamp has quite a clever interface that allows you to resize your partition and then stick in your Windows CD, reboot and install. Also around this early stage it gives you the option to print out a PDF of instructions, to use whilst your new Mac is incapacitated. I foolishly decided not to print out the PDF (or transfer it to another machine - since we don't have our printer at the moment) and so when I got to the 'Which partition do you want to install Windows on' screen, I was unsure of which partition to choose. So, I cracked open my laptop did a quick Google search and found out that I should pick the partition that is labelled "C:". I picked this partition, with vague alarm bells ringing that the partition didn't seem to be the same size as the partition I had created back in Bootcamp (5GB). I pressed on nonetheless. I set it off formatting the partition and was surprised at how long it took to format a 5GB partition. In fact I started it, went out, came back home and it was still going. I began to worry slightly. I decided to abandon the install and reboot to OS X and check that everything was still working. I power-cycled. The machine booted from the CD again. I Googled for how to remove a CD from an iMac when you can't boot into OS X (hold down your mouse button for those not in the know). I then rebooted only to be faced by the horrible screen that told me the iMac couldn't find a partition to boot from.
It turned out that I'd completely wiped the disk of existing partitions. Through luck rather than judgement, just before trying out Bootcamp, I'd decided to try out Time Machine, so I had a lovely shiny backup to recover from.
Hopefully this might serve as some warning to anyone who thinks about trying out Bootcamp - make sure you print out the manual that is offered to you, and if a partition size looks wrong, it probably is!