Is digital contamination that big of a deal?

Is digital contamination from our servers, DAC's etc... that big of a deal as far as that alleged "digital contamination" being transferred from whatever digital component into our other gear?
I had a fellow 'phile demo me last week the difference on his Maggie system with cable/internet box on and off.
There is a diff, nothing I would lose sleep over but its there.
I live in a big city with humungous power transmission lines about 3/4 of a mile away , From about 10AM to about 7pm there is a steady decline in my system, again not the end of the world but noticeable .
I've found MIT Z PC with its filter modules to help some.
"I've come to realize from firsthand evidence that Everybody's system is Absolutely CHOKED with all manner of electrical noise."

From my experience, I would say if you want the best possible sound our of your gear, noise issues associated with digital gear must be addressed on way or another.

IMHO, noise associated with digital gear is in most cases the secret reason why digital gets a bad rap with audiophiles, not the gear or format itself.

So best to consider it an issue and address both noise levels in the wiring and in the air.

Here are some things to cover:

1) keep physical space between components, and digital gear in particular

2) when in doubt use power cords and ICs that offer isolation/shielding from noise

3) If possible, plug analog source and amplicication components into a separate outlet from digital gear and from any other inherently noisy home items, things like flourescent lights, microwaves, computers and peripherals, etc. Separate circuits are even better if possible.

4) Do some resaerch on gear before buying to determine if users report any unusual noise issues with specific digital or switching gear like Class D amps. Newer design Class D amps tend to have better noise controls designed into them than the early models from just a few years back.
How big a deal it is depends on the quality of one's audio system and it's ability to resolve fine detail, as well as the listener's ability to discern small differences.

Good point Twb2, like a drop of food color in a glass of water compared to that same drop in a 10 gallon container. In some systems, just doesn't matter, and others can be a problem.
Harry Pearson recommended turning off your CD player while playing vinyl 25-30 yrs ago! But I never heard a difference. Either my system or my ears aren't resolving enough I guess.