All water, well or municipal, has some microorganisms in it. Especially by the time it flows out of your faucet. They are rarely pathogenic (or at least not in enough quantity to be), but could infect your beer. It's a risk I wouldn't take.
I'm on a well and any water that comes into contact with post-boil wort or related equipment/vessels gets pre-boiled. An electric kettle comes in handy for this. Out of ~20+ 10-gallon batches, no infections yet and I plan to keep it that way.