For example a family member installed a legally sold 'electronic
thermostat' to better control the heat in their bedroom. It did a good
job of that. But ...........

Unfortunately it emitted RFI (Radio frequency interference) that
interfered with the bedside radio in another room; even when it was
tuned to a local radio station!

We have since removed it and relegated that thermostat to another
person's garage where it does not (so far) cause interference! But one
does wish the regulatory authorities such at he FCC in the USA and the
Canadian Dept. of Transport etc. would not permit the sale of these
interfering devices which include certain light dimmers etc.

It appears that just because something is UL (Underwriters Labs.) or
CSA (Can. Standards Assoc.) approved and is therefore 'safe' it may
not be free from causing interference! Also some incompatibilities
occur. Yesterday visited the lamp/light fixture show room of an
elecrical supplier and during discussion the topic of NOT using
dimmers with CFLs came up. Apparently some of their customers are
still not aware of that!