honda-odyssey.com became odyclub.com after they received a similar letter(s) sometime last year. The site owner didn't transfer the domain name to Honda, nor would I without compen$ation worthy of the name they neglected to register.
Not sure whether they make any distinction between .com and .org sites, or whether they've made it to any acura sites yet. I haven't seen anything mentioned on the TL or CL sites (knock on wood).
They do have the right to protect their trademarks, but I'm not certain whether it matters if the name used can reasonably be inferred by the casual surfer to be actually associated with the company itself.
From a PR/Marketing standpoint, it's a mistake to snuff out the enthusiast sites. Sounds like from the final posts in that growing thread that they're working it out, tho...maybe a "not affiliated with Honda" deal going on there, along with some promises not to turn into a slam-the-company-daily site?
Plenty of lawyers around here to comment.
(btw, I think the suggestion for the users not to email or act until+unless the site admin asks for that effort makes sense)