Although the mechanism by which niacin or one of its metabolites induces hepatic injury is unknown, evidence exists to suggest a dose-related, direct toxic effect rather than an idiosyncratic drug reaction.
This is in reference to the slow release form, but my guess is that you could effectively mimic the dangers of the slow release form by frequently taking large doses of the regular (crystalline) form. A kind of "manual slow-release".
Also, note that if you are an under-methylator, taking niacin strains your system further by eating up more methyl groups.