If you sit ten Nintendo fans down in a room and ask them to debate the merits of the blue / spiny shell, then you should grab a comfy chair, some popcorn, and enjoy the ride. Some argue it's an excellent item and a great leveller, others suggests it's an abomination, and plenty sit somewhere in the middle.
Nintendo has kept it since Mario Kart 64, so clearly it's not going anywhere no matter how much some complain online. In some respects the game wouldn't feel the same way without it, as it's a continual source of both anguish for leaders but also joy for the chasing pack. In multiplayer it's undeniably satisfying to advise a speedster buddy that their race is about to go horribly wrong.
For Nintendo, though, it's an item and aspect of design that simply works. ARMS producer Kosuke Yabuki was also the director of both Mario Kart 7 and Mario Kart 8, and he explained to Eurogamer how he sees the dynamic of the item, and also states that experiments in which it's removed haven't worked out.
Something I personally really consider is the human emotion element of the play experience. So for example playing Mario Kart - if you have something that feels unfair or makes you feel frustrated or makes you angry... Everyone is different in that respect. What you will feel is unfair might be different to someone else. As far as possible we want to avoid those feelings of frustration.
Because everyone is different, and it's an emotive thing, you can't pin it down with a set formula. Ultimately, in the longer term, although everyone might feel on one particular day that they're so frustrated that they're not going to play any more Mario Kart today - keeping the experience enjoyable enough so that you might feel like that today, but the next day, the next week, you'll still go back to Mario Kart and still enjoy it.
We're always experimenting with what new elements to introduce or what elements can be removed. We have tried - or we are trying - to see what the game's like without the blue shell. When we've experimented without the blue shell, actually it feels like something's missing. Like there's something not quite enough in the game. So for now we've kept it in.
You know, sometimes life isn't fair. Sometimes in life you have something where you feel that's not right, and that's frustrating.
It's a pretty fair and honest answer - there's no shying away from the fact the item can irritate players, but it's also part of a balancing act so that chasing players always feel like they have a chance. Mario Kart remains a game where skill matters, of course, but luck and good fortune play their part.
Let us know where you stand on the blue shell item in the comments.