|Originally posted by Hogan
Although I do not know how easy, or if it permitted, to trademark legally a symbol of a plant, or to trademark a family-crest that is widespread in Japan, as Chris alluded to. This link further shows that just in this family, over 25% of the families of just one particular family in Japan uses it.... But I am not a lawyer....
Checking around, I note that the name cited on the page above ("Goto") is used by somewhere around 400,000 people in Japan - which would mean that a quarter of them (100,000) would use the same crest as Toyoda. This doesn't include the 3 or 4 hundred thousand people actually named "Fujiwara", among whom use of the crest would probably be more common, and other people with some kind of connection to the original Fujiwara family that have adopted the crest (like Toyoda). I would think that even a conservative estimate would give you well over a million Japanese using the crest as their family emblem.
Of course, anything can happen in a courtroom, especially in the US where most legal authorities have no idea of what you'd be claiming trademark rights to, but I don't imagine that it would be all that hard to make a strong case that the crest exists in the public domain and has done so for hundreds of years. But I'm no lawyer either