Definition:
In a traditional product liability lawsuit, a plaintiff has to prove not only that the defendant's product caused an injury, but also that the defendant was somehow negligent; perhaps the product was poorly designed or didn't come with an adequate user manual.
In a strict liability case, the plaintiff only needs to prove the defendant's product caused an injury - the defendant's negligence isn't necessary for a plaintiff to recover.
Strict liabilty is reserved for "inherently dangerous" activities or products. The classic example used is that of a circus: If a lion escapes and injures an audience member, it doesn't matter how strong the lion's cage was, or how closely the lion was watched.
The reasoning behind strict liability is to hold whoever engages in a dangerous activity - demolition, transporting hazardous materials, using dangerous machines, etc. - accountable for any damaged caused by that activity.
Pros:
Strict liability protects the general public from dangerous activities and equipment. Industries covered by strict liability use extra caution in their activities, as they know they'll be held liable for any injuries they cause.
Cons:
Defendants covered by strict liability are held liable for injuries they cause, even if they weren't negligent in any way.
The Controversy:
As you may have guessed, industries covered by strict liability don't think it's fair that they can follow proper safety procedures and still be held liable in case of an accident. Advocates of strict liability counter that the price for being allowed to put the public's safety at risk is being forced to shoulder the costs of any accidents that occur.
For More Information:
Alternative Rules For Determining Tort Liability: Strict Liability