In reply to mmmhumous:
Spurs have never been used for Scottish winter climbing as far as I know and haven't been used for tooling or continental mixed for many years. They are essentially considered cheating because you can sometimes rest by doing bat hangs off them or heel hook very small holds when doing moves. You can see in the video that he's using the spurs a lot of the time, particularly on the hanging ice blobs. Without them, I guess he'd have to use fig 4s/9s instead and I can say from experience that heel hooking makes things a lot less strenuous (it's sometimes possible to heel hook on tooling routes even with just a rubber heel, if there's a half decent ledge).
There's also the added risk of serious injury as others have said.
In fact for pure dry tooling outdoors most people who have purpose built or DIY fruit boots don't have any pointy bits on the heels at all, i.e. just have a five point crampon piece at the front. You simply don't need the heel crampons and it's safer not to have them, particularly when doing fig 4s/9s. Which makes me wonder if heel crampons (as opposed to spurs) are used/allowed in UIAA comps, never though to pay attention to that.
Post edited at 20:55