I don't really have a compelling argument to prove that using multiple partitions is better or a performance booster.. to me it's just a much neater/more effecient way to setup your hard drives.. In my main PC I have a 160GB HDD and a 500GB HDD.. I have a total of 4 partitions.. 2 on each disc.. 1 for XP, 1 for DATA, 1 for Windows 7 and 1 for Games... XP is on one HDD and 7 on the other.. I have NEVER since I started using computers back in 1997 had an instance where I wiped out 2 partitions while installing an OS.. I have to agree with Kyle there.. that's just not possible not unless you did it yourself.. as he said, a computer will only do what the user tells it to...

As for viruses, I haven't had one in at least 8 years... (knock on wood)..

Unplugging your drives isn't a bad thing or the wrong way to do things.. it just seems like an extra uneccessary step to me.. having them all plugged in at once isn't going to hurt anything.. I do agree that when testing a Beta OS one must use a little bit of caution (that goes without saying) but I wouldn't take it to that level.. Installing a Beta OS isn't much different than installing a finished OS as far as setting it up goes... you go through the same setup process with the Beta as you do with the finished product in most cases so I don't see how that is reason enough to unplug your other HDD before you install.... Just because it's a beta OS doesn't mean it's automatically going to brick your other HDD.... especially if you install it to a whole seperate drive.. I guess my view on that is it's just a whole lot of extra wear and tear on the HDD.. plus with SATA connectors being small and not exactly the strongest pieces of plastic in the world that's just asking for the connectors to break off in my opinion.. but I guess as they say.. to each his own..
 
As far as wiping out two hard drives goes, I was using some Maxtor installation software. I followed the instructions to the tee, but had two hard drives plugged in and they both got formatted while I was only trying to format one. It must have been some sort of internal connection or something, but I did not instruct it to do that. Since then, I always isolate drives, especially while doing installations, it's fail safe.

It's not really a big deal or much wear and tear and I only switch them back and forth on rare occassion and while doing setups. So it's not really a problem for me.