IMO it is complete overkill, every passenger plane has hundreds of mobile phones, laptops, tablets and sundry other equipment being carried by the passengers so how a few mobile phones in the hold are going to cause problems I have no idea!

I wondered about that, too - that is, why can a passenger take a mobile phone on board but there can't be one in the cargo hold. After looking up the risks of lithium batteries, I can understand it. There are a number of dangers, particularly if they get hot, which they probably would in the cargo hold as opposed to the cooler conditions where the passengers are.