I did see honour system stalls but they were pretty rare considering the size of the area. They were more like curious exceptions rather than the norm. They were also geared up to sell at volumes that didn't suit the bike, so too much to carry.
I got the impression from the article on Switzerland that this was more of a way to do your shopping, so sensible quantities not vast bulk purchases.
Incidentally I did not stop to freeload a single strawberry. On a bike with nobody around this should have been simple, there weren't even any barbed wire fences. However, my riding buddy - also a non-American tourist - was not so keen. The reason why was a simple one - 'don't they have guns in America?'.
Actually they have guns in Switzerland too and there is a lot of national service practice going on at the weekends. In fact weekends are quite wonderful in Switzerland as the shops are closed and people go out and do things including going to honour system stalls. The guns though are quite terrifying if you are cycling as you can turn a corner on a descent and feel like you are suddenly in a firing range (rather than right next to one).
I have to say that the Californian produce looked good but was not that good when I bought it in the shops. The land of plenty turned out to be quite expensive and bland to European tastes. Meanwhile, in Switzerland, the roadside appearance of plenty was not so good but the food bought in shops was as expensive as everything is in Switzerland (so no surprise) but delightful to taste.
The relative abundance of Swiss roadside honour stalls doesn't just say things about how honest people are in squeaky clean Switzerland, it also says something about the produce being of value rather than bland.