I've heard some vague remarks about G penalizing sites that get a lot of links really quickly. Is about 500 a month considered worthy of penalty? And does this apply to sites in the sandbox when they come out several months later?
It would be my guess/experience that older sites that are well established can take a sudden jump in links better than young sites, however I don't think anyone could quote figures of what is/isn't acceptable.
Another concern is: say nuclear fusion was perfected and some site at berkley started getting 800 new links a day. How does G even determine legitimacy? Perhaps this only applies to guestbook/forum spam.