The company made enormous profits from the drug while it was selling it; it was highly effective for its on-label purpose and had no known dangerous side effects. After finding that they could be responsible for causing heart problems in patients taking the drug, the company pulled it for ethical reasons and as a means of protecting the company form legal and financial liability -- ongoing cases would have made the drug unprofitable, even with proper warnings (or so it seemed). Then, rather than pursuing cases that it was clearly winning, Merck spent less than one year's profits to settle all pending cases, coming out very much on top financially and in the clear legally. The fact that competitors still offer similar drugs suggests that Merck might actually have been to conservative in its response to the Vioxx issue. A re-release...

The plaintiff must show that the activities the defendant is engaging in cause a material difference in the use of the plaintiff's property, and that the defendant's actions are not standard, necessary, or otherwise legally protected. The defendant can resist the suit by proving any of the above. A common business tort is theft of intellectual property; plaintiffs must prove that a documented original concept/idea/image/etc. Of their creation was utilized by the defendant without permission, generally for commercial purposes. The defendant must prove a fair use defense or the receipt of authorization if the idea was original to the plaintiff.