and it's not like Ferrari are saying "do what we want because we are prima donnas and you'll be sorry if you don't".
they are saying that they entered the sport for a reason, and have stuck with the sport this long for a reason, but that if the new rules go into effect, their reason for participating will no longer be there. they want to compete at the highest level, and up until now, F1 has been the "pinnacle of motorsport", but under next years rules it wont be, and it's completely fair play for them to pass on participating in a series that is a joke.
and on the "conspiracy" side of it, maybe if they skip 2010 they can "cheat" by working on their 2011 car in secret for 2 years. just putting that out there before the haters do. :P