Just noticed a discussion on Nopesport
about use of SI air cards. The discussion there looks to be largely around the fairness/unfairness of whether events should allow both touch-free (or contactless) and touch (contact) SI cards in the same race.
I haven't seen SIAC (touch-free) discussed much on AP yet, maybe because the number of events that have used them in NA have so far been few, and those that I've seen have issued loaner cards to all participants.
While the Nopesport discussion goes through many of the expected arguments for and against mixed punching, a couple of things jump out at me:
1. If we're going to be making a transition from touch cards to touch-free cards then it does seem necessary that there will be some amount of a transition period. That or else we scale up the model where organizers continue providing touch-free cards to all, which seems somewhat unlikely.
2. For the course-setter, touch-free punching has the benefit of being able to go back to tying controls to existing objects such as trees where available and not having to lug around so many control stands just to support the SI control units.
3. While arguably less significant for foot-O, touch-free punching makes a huge difference in the ease of punching in ski-O and MTBO, where the competitor's hands are already fully occupied. In MTBO it often seems necessary to unclip from a pedal in order to avoid falling over while waiting for the SI to register.