... and then using their Payback loyalty cards at every opportunity.
Don't get me wrong: many Germans hold out on loyalty cards and some people may indeed use cash to avoid a paper trail, but you make us Germans sound like mythical privacy-minded creatures which the vast majority of us is decidedly not.
One example is browsing Google Street View and seeing how many buildings & houses are blurred out in Germany due to people sending privacy requests. I don't think I've ever seen that in Australia, but I keep encountering it when planning my trips to Germany. 3% of Germans opted-out of their house being included in Street View - a low percentage of Germans, but still crazy high compared to the rest of the world:
https://googlepolicyeurope.blogspot.com/2010/10/how-many-ger...
I would respond to their arguments but I'm not sure they're making any and I don't think they're actually disagreeing with me (or even understanding what I'm saying).
Even in little things: like Germans using cash because they don't want to create an electronic credit card trail of where they were, or walking through Munich train station and seeing Snowden in all the news headlines (in 2013), while back home he was getting nowhere near as much news coverage (and certainly not the front page headline).
I don't know if any of this applies to Mailbox.org, but as a marketing phrase it works for me.
[I'm Australian, but an 'aspiring German'.]