I forgot to do the most basics of basics when looking into this, I didn't check if this site was still hosted by SEGA. So I pinged dreamcast.com and lo' and behold http://22.214.171.124/
was the IP I got. It links to a cPanel set up page. I then pinged SEGA.jp and got the IP 126.96.36.199, SEGA.com: 188.8.131.52, Sonic Team: 184.108.40.206. All SEGA sites are no where near the IP range of dreamcast.com. Running a trace on this IP brings us right back to square one with DimeNoc/dizinc.
SEGA.com is run from San Francisco under their own, internal servers. SEGA.jp and Sonicteam.com are run from inside Japan, as you'd expect.
So to sum up, it's a site not on ANY of SEGA's servers, it's supposedly a Japanese site running on a shared server in Orlando, emails set out are from a dizinc email address, uses Gmail as a front for a Dreamcast email address, the site poses as an official website (including copyright marks from SEGA). It's fake, don't use it. If you have used it, as a few of you have, hope this comes to nothing.
Emails sent from dreamcast.com are emails actually sent from a dizinc.com email address, which forwards instantly to DimeNoc. I believe DimeNoc are a hosting company and are actually just the service provider for this scam.
This hit Digg's front page an hour ago, which was plenty of time for the registration page to go down. Looks like the people behind this just missed a literal gold mine of email addresses. But they took the page down, probably after getting a certain number of emails anyway, which I'm sure will get sold on to some SPAMSPAMSPAMSPAMSPAMSPAM companies. Oh happy days. It was a very believable scam, however. One which even I fell for, let this be a lesson to you all. Don't trust the internet.