TechCrunch recently broke a story about Network Solutions hijacking users' unused subdomains for advertising. It seems to have only applied to people using Network Solutions for their shared hosting, and seems to have been removed now. (None of the IPs I tested on the same machine returned advertising for their non-existent subdomains) And on top of that we know that anyone who is on shared hosting is pretty easy pickings anyway, so this would seem to be a non-issue regarding security.
But Network Solutions doesn't exactly have the cleanest record in terms of ethics and there isn't anything technically stopping Network Solutions or any other company operating NS servers for your domain doing the same thing even if they're not hosting your content.
So given that this is a security blog, and definitely not an ethics blog, why am I talking about this? Because it introduces security problems.
As I talked about in previous posts about cookies, they are almost always sent to subdomains, and if your DNS operator implements something like this then all your users' cookies are being sent to your DNS operator's servers, which means that your cookies are taking two specific network paths which both have to be secure for your credentials to remain safe (three if you count that the DNS request has to be safe).
Now you may trust that your DNS provider isn't going to do anything intentionally malicious with the cookies, and are probably making the valid point that worrying about people having owned other networks being a vague and impractical threat to defend most websites against, but there is a much simpler risk involved here.
Network Solutions has made no effort to secure these pages from XSS, and why would you? They're essentially brochureware domains. Anyone who has probed a parked domain for XSS has probably seen that they have plenty of XSS holes, and the pages Network Solutions served for non-existent were the same pages that they serve on parked domains.
So after googling to find a parked Network Solutions domain, I found it was unsurprisingly trivial to XSS it via the search field.
So; how much do you trust your DNS operator?