They may not be dangerous as properly packed cargo... but imho they are inherently dangerous as the average Joe does not see them as such...
case in point... a few years ago (before i knew better) ordered a couple of spare batteries for my Olympus camera. I was actually shocked when they arrived in a manila padded envelope marked as 'gift'. Not even isolated terminals and freely clinking around the bag.... I emailed the seller and they could not have cared less so I filed a report with eBay and explained that they needed to have a clear instruction on sale/shipping of these batteries.
Just think how many of these little 'gifts' are flying in your cargo hold daily
