Very little of it. When you see a million IPs systematically working their way through your URL space, it's pretty clear that there's a central control node behind it all.
It's an experiment. Compared to the text-obscuring popovers that are prevalent elsewhere on the net, it seems pretty low-key; as far as I know, this is the first complaint I've seen. I don't know if we will continue experimenting with those or not...better ideas for getting people to subscribe to the site would be more than welcome.
The kernel does not copy every page, but it does have to copy all of the VMAs. Setting memory to COW (which can involve changing a lot of page-table-entries) is not free either. I guess I could have mentioned copy-on-write explicitly, but I do not believe that what I wrote was incorrect.
I hate to blow our own horn, but I'm gonna...if you are interested in seeing this kind of kernel-development data mining, fully human-written, LWN posts it every development cycle. The 6.17 version (https://lwn.net/Articles/1038358/) included the buggiest commit and much surrounding material. See our kernel index (https://lwn.net/Kernel/Index/#Releases) for information on every kernel release since 2.6.20.
Being used to validate stolen card numbers has long been a problem; we've had to put in a number of defenses to fight our way off whatever list of "easy sites" these folks maintain. I hadn't thought about the "change card" path though...another bit of time spent away from what our business is really supposed to be doing...
Something broke down somewhere ... I got emails a while back about the acquisition and giving options about whether to go along with the move or not.
Since Gusto is our payroll provider, I didn't see a reason not to do that... hopefully there will be less finger pointing the next time something goes screwy with the 401k transfers.
The "compliance officer" at Bright Data, instead, offered me a special deal to protect my site from their bots ... they run a protection racket along with all the rest of their nastiness.
We do try to spell things out and/or link them in LWN articles to make the context available, but some things we just have to assume.
Additionally, spelling out "Berkeley Packet Filter" is not going to help any readers here; BPF is far removed from the days when its sole job was filtering packets, and that name will not tell readers anything about why BPF is important in the Linux kernel.