It’s an old standard that body copy should have a line length shorter than 75 characters per line. But on the web, the acceptable number is higher. From a post I did today at Viget, I cited research that demonstrated that users can easily handle 95 characters per line or higher:

What is the new standard? Tough to say, but 100cpl seems to be within the range of feasibility. There may be a good opportunity for some new and more thorough research in this area that could offer some valuable new insight.

I suspect this is due to print being a largely-vertical medium, and the web (especially since widescreen became prevalent) is more and more horizontal.