I doubt you'd lost a legal battle over the use of that name on a group on a random website. As long as you're not trying to make money off the brand it's extremely unlikely that there would be any legal action from anywhere. There are groups on pretty much every social site with groups named Audilovers, Lady Gaga's girlfriends, Microsofthaters, Applelovers, bananacakeleague or whatever...
Using the name 'Stardock' implies official approval/association with the company.
Geeesh, I guess Ferrari and every other popular big company have a huge amount of approved/affiliated fangroups on sites like facebook then...
If Stardock REALLY think it's a threat to their reputation I'll make darn sure to never mention the company or brandnames to anyone, just to save them from the risk of someone believing there's some approval/association with me... Maybe it's safest to stop buying/using the software too, that should entirely eliminate the risk of anyone thinking I have anything to do with the company.