@Doctor WhoW3bbo: I think every electronic device emits some level of EMI (electro-magnetic interference). The degree of shielding and power involved will vary by device, manufacturer, etc.
Indeed, and that's the basis for banning the use of electronic devices during take-off and landing of an aircraft. In practice, almost nothing you carry actually has much chance of interfering (even a cell-phone not set to airplane mode), but from the FAA's point of view it's easier to ban everything than to try and determine exactly which devices are safe and which aren't, and from the flight attendant's point of view it's a lot easier to check if someone's using a device rather than what device they're using and whether it's on the safe list.
@elmer: An acquaintance of mine had their computer in the kitchen, near the microwave. This created some weird interference effects on the (CRT) monitor whenever the microwave was being used. This did not speak well of the shielding of either the monitor or the microwave.