Not only don’t these things work very well, now it can land you in hot water.
In California, a lady buys $10 amplified rabbit ears; Amp starts to oscillate and interferes with Verizon cell service. FCC investigates and the lady is cited for: “The operation of an intentional, unintentional, or incidental radiator”
http://www.fcc.gov/eb/FieldNotices/2003/DOC-292933A1.html
It gets more interesting; she could be subject to real penalties:
“Action may subject the violator to substantial monetary forfeitures, seizure of equipment through forfeiture action, and criminal sanctions, including imprisonment.” (emphasis added)
There is going to be more and more of this. Several things are converging. You have overall antenna usage skyrocketing and big box discounters trying to address the market with the cheapest methods possible. With the explosion of smart phones, the spectrum is getting more crowded and as the value of the licensed spectrum becomes more valuable, wireless carriers are gettting more protective of their properties.
Antenna buyers: not a good time to go for the low bid.