Because magic.com doesn't have an A record. If you click on the "free" link, the registrar (moniker.com for now) will tell you that it's taken. I know this is disappointing, but I haven't found a good way to do bulk whois for millions of names, DNS is much easier.
How about doing a DNS lookup but for a SOA record type, instead of an A record? I'm fairly sure that will either give you a record or an NXDOMAIN.
$ dig magic.com SOA
[snip]
magic.com. 21600 IN SOA auth03.ns.uu.net. hostmaster.uu.net. 990605 21600 3600 1728000 21600
That sounds good, I'll look into it.
Ya, I got excited and tried to buy magic.com too :(