There is an old saying out there:
There are two kinds of people in the world - those who have lost all of their data, and those who will!
I now count myself in the party of the first part. To make a long story short, I decided to upgrade to Windows Vista CTP a few weeks ago. While Vista was great, there were some compatibility problems with Virtual PC (which I need for my job) so I had to go back to Windows XP SP2. During this process of formatting my drives, somehow, my external drive got whacked!
In the end, I was able to recover most of my files (spent the entire weekend doing so), but I was forced to do a post mortem on why this happened.
Basically, it was because I didn't follow my own procedures on proper backup of my files, but a contributing factor was my desire to try out a new set of technologies - and then re-ghost my machine when I needed to go back and do real, customer work (how many times has this happened to you!)
We'll, I just noticed that the new Visual Studio ORCAS CTP is being released as a VM! This is fantastic news, as it means developers can work on the new technology, without messing with their primary machine configurations - and eventually having to re-ghost their machines when things go wrong.
I hope we start doing this for all of our new CTPs and Beta products. While it does create longer download times (+5 hours on a T1 line), I think it will lead to a greater acceptance from programmers who don't want to install software on their primary machines.