Major printer manufacturers sell printers at or below cost. They make their profits from selling the cartridges. Formerly, once you bought your expensive new printer you had no choice but to buy one of their cartridges after yours ran dry. By using compatibles you are cutting into their primary source of profit. Because of this, they will threaten to void your warranty if you use compatible cartridges. They are simply trying to protect their own interests anyway they can. It is however strictly ILLEGAL for them to do so. They CANNOT VOID YOUR WARRANTY simply for using compatible cartridges. There is no reason that you should not use compatible cartridges. They work and will save YOU money.