Mmmmmmm
This thread is making me think that everyone should get in some good paceline practice.
Obviously it's easier to learn when you're young and full o' beans. And it may be harder for slower riders to find a group of people who want to ride paceline.
But the basic skills are ones that every rider should work on periodically. Maintaining a consistent speed; holding your line; signaling hazards both verbally and with hand signals; bike-handling skills and reflexes; group manners; listening to one's own body to know when to hand off the pull. Whether one normally rides alone or with others, it's important to have all these skills for traffic situations, and sympathetic pacelines of riders of similar abilities are one really good place to develop the skills.
Speed comes from what you put behind you. - Judi Ketteler