This file demonstrates that a new ggplot2 geom I've created--which puts rug fringes on the top/right--seems to plot just fine when sourced from a single script.

geom-rug-alt-demonstration.R

geom_rug_alt <- function(mapping  = NULL, 
                         data     = NULL, 
                         stat     = "identity", 
                         position = "identity", 
                         ...
                ) 
{
  GeomRugAlt$new(mapping = mapping, 
              data = data, 
              stat = stat, 
              position = position, 
              ...
  )
}

GeomRugAlt <- proto(
  Geom, {
    objname <- "rug_alt"

    draw <- function(., data, scales, coordinates, ...) {  
      rugs <- list()
      data <- coordinates$transform(data, scales)    
      if (!is.null(data$x)) {
        rugs$x <- with(data, segmentsGrob(
          x0 = unit(x, "native"), x1 = unit(x, "native"), 
          y0 = unit(1 - 0.03, "npc"), y1 = unit(1, "npc"),
          gp = gpar(col = alpha(colour, alpha), lty = linetype, lwd = size * .pt)
        ))
      }  

      if (!is.null(data$y)) {
        rugs$y <- with(data, segmentsGrob(
          y0 = unit(y, "native"), y1 = unit(y, "native"), 
          x0 = unit(1, "npc"), x1 = unit(1 - 0.03, "npc"),
          gp = gpar(col = alpha(colour, alpha), lty = linetype, lwd = size * .pt)
        ))
      }  

      gTree(children = do.call("gList", rugs))
    }

    default_stat <- function(.) StatIdentity
    default_aes <- function(.) aes(colour="black", size=0.5, linetype=1, alpha = 1)
    guide_geom <- function(.) "path"
  }
)