If you want to use internet on your music PC, fine. I'm not. Nor will I use anything that requires me to access the internet just to get it to work.
It's not fear. Experience has taught me that I don't deal with any of the things mentioned in this thread on my music PC. I don't do this for a living. But when I do go into my "studio" :) I make music.
With Win7 Pro, maintenance is almost zilch. I get Sonar working, and don't change anything until an update comes along.
And knowing what I know, (and not knowing what it's like to have to depend on my studio work as my family income), that if I did have to depend on this for a living, I still wouldn't hook my main music making PC to the internet. I'd get another PC sitting on the side with a USB hd and transfer whatever I needed right on the spot. Why would I want to install Dropbox software on my main music PC? Or have Win Defender running? Or Firefox/Chrome installed on it?
But that's just me.