As it happens, I run a lab that measures the conducted and radiated electrical noise emitted by products that need to meet certain government-imposed standards before they can be marketed. Check my Profile.

1) Switch-mode power supplies are indeed inexcusably noisy. Having several of them in the same rack would indeed create a bad situation.

2) The noise these power supplies generate is conducted back into the AC mains they are plugged into.

3) If a bunch of these noisy phuckers are plugged into a simple power-bar, they will definitely pollute each other's AC supply.

So far, any power conditioner manufacturers reading this are nodding, and grinning.... now comes the bad news...

Unless [u]each individual outlet[/u] in a power conditioner has it's own filter and surge suppressor, anything plugged into this device is going to share it's noise with anything else plugged into the same device.

For the posted price of three easy payments of $99 each, my experience in the industry suggests that there is only one full set of filters in this box. In other words, the outlet side is likely to be protected from noise that originates on the AC mains that the protection device is plugged into, but any equipment plugged into the outlet side of this device is probably not offered any protection from other devices which are also plugged into that outlet.

To elicit the proper response, I will suggest this creates a situation in which the devices plugged into the outlet of such half-assed gear is safe from the potential hazards of the river water, but they're left to drink each other's piss! Yummy!