I strongly agree with Andy Putman's comment.
I also am very annoyed that my account was copied. My name is my academic "brand", so to speak, so I like to have control over where I have accounts.
Listing people who have never heard of, visited, or endorsed your site as users, with fine print saying that they have not actually participated yet, is a dishonest and exploitative practice. Since you have chosen to begin your relationship with me in this way, there is no chance that I would ever use your site.
We unfortunately cannot really "remove" all imported accounts as many would like to reclaim their accounts.
Yes, you really could. Listing someone as a user of a site without their permission seems close to the border of legally actionable behavior. It is not a good way to run an academic website.
Added to address quid's comment: Content contributors would certainly be better. (And I agree that their use of the content is completely unobjectionable.) But in my case, there is no content. Therefore I can't see that my name is being used there for any legitimate purpose. Rather, I feel, as Andy said, that they are trying to make use of "the Pete L. Clark brand".
More to the point, I just don't feel that things are being done in good faith. The site currently says that I first posted three years ago. Any way you slice it, that's simply untrue. They also speak in terms of accounts being "reclaimed", but come on: that's double-talk.
After I wrote this answer, I spent more time searching the site, and I can't find any information whatsoever about who is running it. The founders of the site have taken care to stay anonymous. (Added: More precisely, 2/3 of the founders are pseudonymous. The non-pseudonymous founder is a minor.) It seems that they want to be very careful about the use of their names and reputation. The confluence of this and taking my name and using it to promote their site without even contacting me (hey, if you want me to join your site, how about asking me?) seems hypocritical and disrespectful.
Further Added: @Dimensio1no: "the moderators and their names are accessible quite easily from the "Special users" tab under the "Users" page." Two of the three "Super Administrators" are listed only as Dilaton and polarkernel. Those are not names of people. In fact I received an email message from one of these, which said that s/he keeps anonymous for a "good reason". A serious academic site is one which is run by people who disclose their real names.
It also says
First posted (imported): 3 years
I have never posted anything on your site. What is that you are importing? And how can anything be done 3 years ago on a site that has existed for less than a year?
I am currently looking at the page
If you really want to argue that there is no implication here that I am a user of your site, then we are going to have a problem. Why did you put my name here in the first place? If it is really only because I was listed as a user on another website: that's a problem. I explicitly gave Stack Exchange permission to list me as a user on certain of their sites (and not on others). Taking all the names on another company's site and importing them on your own site is not a good faith action. Moreover you don't even inform the people that you are using their names in this way.
What is the (full) name of your site's legal representative?
Yet Further Added:
As Mr. Abhimanyu has failed to identify anyone else by name as being owner and representative for the site, I will assume that he is responsible for it. Let me respond to his points:
1) Deleting all "imported users" who have not contributed and TP.SE user was a good start. Thanks very much for that. However, in that you are still claiming other users, the problem has not gone away.
2) There seems to be some terminological confusion.
I said "founder", not "moderator". Those are completely different things, and the fact that the difference is obscure both on the site itself and seems not to be not completely clear in Mr. Abhimanyu's mind is not a good sign. Everyone knows that Stack Overflow and then Stack Exchange was founded by Jeff Atwood and Joel Spolsky. This openness and direct dealing with their clientele was certainly a key to their success. I am kind of surprised that some people hear seem happy to support a site which is untransparent (and in my opinion, even somewhat misleading) about its own provenance.
An "imported user" is still a "user". The language implies that they have used the site. Using this language and then correcting for it later on the "user page" (!!) is not complete clarity; it's double-talk. Mr. Abhimanyu wrote
I do not wish to repeat how the fact that you do not use, contribute to, or endorse the site is the second-most clear thing on the page.
Even by your own admission, it is more prominent that you have a page with title and existence naming people as users of your site. Whether the parenthetical (!!) sentence
"(This user is not yet participating on PhysicsOverflow, but we hope they will)"
is the "second-most clear thing on the page" is not a point I want to debate. But the language is a far cry from saying "This person does not use, contribute to, or endorse the site". Participation is something I never did on TP.SE, but I did sign in and create an account there. The language of your site suggests that my account has somehow been transferred to PhysicsOverflow. That's factually incorrect, it's legally questionable at best, and after all this conversation I still feel like you are exploiting people to promote your brand.
3) The claim that "Pete L. Clark" is licensed content under the Creative Commons is truly alarming. Even with my "account" deleted on your site, I feel that I will have to consider responding to that legally. Probably my first step would be to consult with an attorney at my university and have her correspond with PO's legal representative. Once more, who is that?