Definately personal preference....
There's really no need to add imo, like PBQ states, salt occures naturally in water(yes that includes freshwater too) and maybe added by your water treatment company(unless of course you have well water - but test for salt anyways) - some goldfish just don't do well with salt at certain levels, you'll see it if their eye's start to bulge and they may get a milky look to their skin. If you do add salt, keeping it about 0.05 - 0.1 should be fine, but I suggest you test your source water(tap) before addition to obvserve it's salt content.
If you're keeping up with waterchanges/maintenance, or use a quarantine tank for new additions , then you really shouldn't have worries of infection(bacterial or parasite).
Just my thoughts......