We just got word that as of April 8th, 2009, CarDomain and StreetFire.net have joined forces as the #1 and #2 social networking sites for automotive enthusists.  Taken from the Press Release:

Each site brings complementary information-sharing technology to the table. CarDomain two million registered users have posted 650,000 active ride profiles with a combined four million aftermarket modifications, all accessible by component type. StreetFire.net brings video sharing technology that enables users to upload videos, view any user-created video online, and embed these videos onto their own sites. This technology has allowed StreetFire.net to reach 250 million video streams annually. Sharing this technology and content allows each site to enhance its current offerings, such as bringing new video capabilities to CarDomain member profiles. Versatility and functionality improvements will also be made, such as offering customizable advertising packages that directly target select consumer groups.

For more info, check out CarDomain, StreetFire.net or TechCrunch