I don't think it's the clutch, but I've heard the slave cylinder is the weakest link. Nissan issued a recall with the '07 Z with some users reporting sudden loss of clutch pedal pressure causing it to sink to the floor. At least one owner got in a bad accident because of the pedal sinking to the floor.
Recall on slave cylinder - MY350Z.COM Forums
I'm surprised this issue exists with the 370Z.