How much time should it take?

Via The Valve, two posts on the historical trend toward longer and longer periods of graduate training: in the 60s, it used to take 4-5 years past the BA; it now may take up to 11 years. The comments in the post in the Valve are also pretty interesting. Commenters mostly explain this trend as a result of the saturation of the market: since there are few jobs anyway, doctoral students draw the process out, trying to get a very good dissertation in the process, something really publishable. I tend to agree (it fits with my experience); what do you think? And how long is too long?