i have come to the conclusion that the purpose of a poison pill is to protect management, not the shareholders. when a company is run by incomptents, and its stock is underperforming, management can use the poison pill to save their jobs from being thrown out in a corporate takeover. but when management acts in collusion with the buyer (after being bribed with the requisite number of shares and options) the poison pill isn't used at all.

in other words, a shareholders rights plan is completely worthless, unless you happen to be an incompetent executive trying to hold on to a job.