If you join a group/paceline, you should know the intentions of that group. If you don't like the group's rules, don't ride with the group. I'm not a fast rider so I stick with groups that set a moderate pace and are fairly tolerant of individual skill levels. On a couple of occassions I've gotten in with a group where I hung on as long as I could but couldn't keep up. At that point I'll pull or drop off telling them that I'm fine and to go ahead, I'll meet them at the shop etc. so I don't hold them up. Wrong group or just a bad day, I'm not going to hold up a group ride / paceline. If I want a no-drop ride, I'll join a no-drop group.