How do you keep the keys apart...?
I have lived in the heart of the beautiful Dutch city Groningen for many years which is known for its bike steeling culture, especially under students. It's one of the safest and most friendliest cities I know but almost every student rides every other students stolen bike… I will admit that after having my bike stolen multiple times I was forced to take part in the “swapping” community as buying new bikes was not an option.
For some this will sound shocking but since we only stole bikes that were stolen before (you get an eye for that), the swapping bike culture kind of resembles the White Bikes Plan that is known in some cities. Except for the lock then ;-)
Many years later I have ridden some beautiful bikes on local tours and marathons and preventing a shinny, hard earned Specialized S-Works Fully to swap owner without my consent is a daunting challenge. This is where my former hometown has given me some lessons.
When I cycle I never take a lock with me! It prevents me from fooling myself I can safely lock it. When I sit at a café my bike stands next to me. When I buy some groceries I try to find another biker to watch my bike and take turns in shopping. It’s a bit cumbersome but the absolute safest way and the positive is you don't carry a heavy lock with you the whole day.
If it would just prevent one bike theft I would be happy since having your bike stolen during a Bike Tour or vacation mostly is a very stressful and sad event.