Comment 9 for bug 850475

As an alternative aggregating style, consider this:
Say you have 3 datapoints with values 100,50,500, and all these must be represented on one pixel.
Suppose the background is black (RGB 000) and the graph is white (RGB FFF). If you want a graph that is filled (entirely colored from 0 until the value), you could draw a vertical line (1 pixel wide) from 0-50 in FFF, a line from 50-100 in "white divided by two" (BBB) and a line from 100 to 500 in "white divided by three" (555).
If you want a standard looking graph (a plot of 1 pixel), you could just put one dot at 500, in color 555.

This way you have a visual cue that there is a high spike: you can see the highest achieved value, and the amount of fade on the color suggests how strong the spike is. this seems very useful to me.

Only catch is, if you have many different graphs on one plot, it may be confusing to see which points belong to which graph. But that's nothing new.