Using DA to point a domain locally or to a remote site still presents the DA server IP as part of the trail AFAIK. Certainly using the DA server NS dislodges more data.
I'm pretty sure some of the spam on my very old ISP email (must be close to 20 years old now) address originated after being propagated in whois, soa, etc from host providers or my very early domain registrations. oops.
Although not instantly or to casual users, can direct correlation to server operator be made with domains. The way info is consumed though, and as time passes analytics available at some of the DNS sites I've used is amazing. Over a period of time though I'd bet the correlation could almost be considered magic in how accurate it can be. Perhaps never reaching 100% accurate, but that's approaching as cameras continue to be deployed -- unless cell phones have already sufficed to stitch it all together. hehe
I think there is a certain amount of info to be had from domains that dead end at the registrar but intermittent whois and other info is swarmed (about like putting a new server online is by port scanners) and stuffed into the data banks. I am confident that if desired, a party could obtain via private companies, every single IP my domains have ever pointed to (along with more info in many cases) probably going back to mid-90s.
I don't much care about that for most domains I hold. However if I don't wish to sell or develop any of them I don't want to be bothered
at all about them. No SEO, no traffic, no email, no offers of any kind. Nothing. Unless they want to spend time and money, track me down, ring to doorbell and make an offer face to face then not interested. hehe Some of the domains I've lucked out in this regard. They have no nameservers assigned at the registrar. Proof positive that no spam coming from them! Not sure 0 NS is possible at the registrar level anywhere these days.
Suppose someone has 20 domains with names that are dubious in and of themselves. Not based on any sort of associated hosting. Say all curse words or topic oriented in some way that is not politically correct.. All pointing to my server IP. If nothing else it could be construed as the server owner/company being sympathetic of whatever people conjure about those names.
IMO, this could have backlash for an IP of the server at least. The rest of the possibilities is only limited by the flaws of humanity.
The parking service sounds interesting, Jeff. I was working off and on with a parking system years ago for the DS I had.
If you tangent to off-topic I will follow since what you describe sounds useful and interesting to me as a domain portfolio owner.