As I go through my team's presentations I take available opportunities to replace bitmaps in those slides with the native graphics features in powerpoint.
And then I found this slide:
At first I doubted that I could replace the bitmap with native powerpoint graphics, but with a little bit of experimentation I made this:
I've attached the deck with both slides: PowerPoint-Experiment-(2007-06-03).pptx
Here's the size difference in the slides: