They are "front-running" available domains so that they may only be registered via NS.
If you search for an available domain at www.networksolutions.com and it is otherwise available to be registered, they automatically register the domain in their name for 4-5 days to prevent registration through another domain registrar during that period.
They will continue to show it as available through their site and will register it to the first requester with $34.99, but a whois shows it unavailable for the next 2 years. 4-5 days later, if it isn't registered, they release their claim on it.
Test it for yourself by doing a whois on a bogus domain name, then doing a search for it at NS and finally running the whois, again.
This is really slimy behavior in my opinion.
Here's a story on it by DomainNameNews
So. Run those "available domains" name searches through another company, for now.
Posted: Mon Jan 14, 2008 2:03 pm