Some scientists are now theorizing that the dinosaurs weren't wiped out by a single asteroid strike, but by a barrage of them. Others are skeptical.

It wouldn't necessarily surprise me. Sometimes asteroids, and particularly large comets, are more of a cloud of bodies than a discrete single one. Recall the multiple impacts on Jupiter a few years ago when it crossed the path of Shoemaker-Levy.

I don't think that what's being suggested is the impact of a "rubble pile" or even a disrupted cometary body -- rather, it's two or more impacts separated by a geologically short interval (years to centuries). I was privileged to hear Gene Shoemaker speak at the Texas Star Party in '92; his talk hypothesized that the Manson impact in Iowa had occurred just a few years after the Chixulub (?) impact in the Gulf of Mexico, greatly magnifying its effect. It's now thought that the Manson impact is unrelated to the K-T extinction, but "comet showers" may have occurred nonetheless -- here's a particularly intriguing mechanism (follow-up post here).

Dr. Melosh who is quoted in the article has put forth some pretty compelling arguments against asteroid induced volcanism. To summarize, the impact energy of the asteroid is much less than that required to produce the degree of volcanism that's often present. Second, the alternate explanations for volcanism - removing of overbearing rock, incremental addition of heat still require a system that is very close to erupting naturally. In which case, why rationalize asteroids as the cause when the passage of some time will do?

Instead, it appears to me that there is an out. If the natural equilibrium of such a system were always just short of volcanism. Then removal of overbearing material would result in some proportional degree of volcanism until a new equilibrium were reached.

course shoemaker levy was't initially several bodies... it got put through the ringer by jupiter's gravity, and then it fractured into multiple parts that had separate impacts