Back in the mid 1970s we spent almost a year discussing and testing the alternatives. Our finding was that the primary should be donated. This was based both on practicality issues and on the base premise that there needed to be one and only one way of initiating the flow of an emergency procedure. Donation of the primary made everything identical it did not matter if the receiver was expecting to buddy-breathe or to use an auxiliary. The procedure changed only when the donor permitted the primary to remain with the receiver and shifted to his or her secondary. With respect to the backup (type, location, deployment, training, practice, etc.) we found that it was the responsibility of each individual diver. We also found that a longer primary hose was advantageous, with a five foot hose being ideal for open water with a single tank and a seven foot hose being better for doubles or diving in an overhead environment.
I donate my primary and choose a backup appropriate (at least in my view) to what I am doing and whom I am diving with. For a single tank on a no-D, openwater dive my favorite is:
Backup choice, location, securing, deployment, etc., ain't nobody's business but your own. But is is very serious business, and input from your fellow team members should always be sought.
Who give a rat's rear end what every agency on the planet and 95% of all divers on Earth do? Surely not you?
Surely not me?
Surely not Peter?