Well, I certainly hope that news.yc users are a bit more than Ricardo-programmed economic optimization automata. :)

One solution to older users having a perpetual advantage would be to implement some sort of aging of karma, or at least of the karma value used to determine throttling. Such a thing would actually be a win in terms of SNR--it doesn't really matter how karmic someone was a year ago, if they have only made low-quality posts/comments in the past month, they should be treated (in the submission system) as a low-karma user.