This is awesome. This story is claiming that gamers were "duped" by Sega asking for Dreamcast serial numbers over the weekend, and that the domain "dreamcast.com" is not owned by the company.
Using amazing internet skills, videogaming247.com has confirmed that Sega does, in fact, own Dreamcast.com. From the whois registry:
Domain Name: DREAMCAST.COM
Shoji Takamitsu (Shoji_Takamitsu@sega.co.jp)
Haneda 1-2-12, Ohta-ku, Tokyo
Creation Date: 12-Jun-2005
Expiration Date: 12-Jun-2008
Give Shoji a ring if you like, just to be doubly sure.
The outcome of registering your Dreamcast on the site is that you're given a Dreamcast branded email account. Dreamcast's tenth anniversary is this year, so rumour is obviously rampant that getting your machine's identity on the list will have another benefit somewhere down the line.