Take what you think is a representative sample of a OW *ONE* RTW itinerary, and price out what it would cost to by the individual segments. You'll see that the RTW fares offer a substantial discount off the "regular" fares. Most of the *ONE* rules relate to placing limits on how far you can go with the RTW fares, but a few of them are designed to prevent too much cannibalization of the regular full fares, such as:

- 7 day advance purchase for 1st int'l segment
- 10 day minimum stay away from home
- must actually circumnavigate all the way around the world

Without the above rules, it would be too easy for, say, a businessperson to take what was essentially a point-to-point business from from their home base to one remote destination and call it a "RTW" trip just for the sake of not paying full price.

So, I can see how attempts to use multiple nested RTW bookings to circumvent the "minimum 10 days away from home" rule could be considered abuse. After all, by doing so, you could turn what is in reality two separate short-duration int'l trips to a single remote destination into two RTW trips for a substantial discount off of full fare.

But short of that, I really don't see why an airline would have a problem with nested (or otherwise concurrent) RTW trips.

I agree that some of the ticketing rules that people get caught up in are arcane. But, at least for the OW *ONE* RTW tickets, it's hard to believe that anyone would purchase one without knowing that it involves a substantial set of detailed rules. Even if you didn't learn them all by rote, I find it hard to believe that someone would buy such a ticket without knowing that they are buying into a product with very specific rules.