I've read
this on N&N, and was appalled by the mentality of most people: They think Finarfin is a wimp.
Here is what I think: Had Finarfin been alone, he would have gone with Fëanor. But he was thinking of the people Fëanor is leading(ironically, Fëanor doesn't care) Those people, although unwilling, still followed the misguided maven. Upon hearing the Doom Mandos pronounced on them, Fëanor still was blinded by his desire for revenge. He simply didn't care!
Obviously, someone has to think about the people. Someone did.
So, is Finarfin really a wimp?
->Elenrod