I figured out how to draw historical track log data from my tracking app onto the Virtual Earth control.  It's a pretty early implementation, but it works really well.  I'm generating transparent PNG images on the fly and using them as the content of a well-placed pushpin. Here's a screenshot:

Don't be confused.  If you've played with the VE API, you may think I'm creating a pushpin for each datapoint.  I'm not. I'm creating one image and overlaying it on the map.

Once you figure out how to take the latitude/longitude to pixel translation to the server-side, it's fairly straightforward.  The hardest part about it is geting transparent PNG images to render properly in IE.  Hilariously, my workaround currently breaks the functionality in anything other than IE.  Just stupid.

Anyway, now I have to resolve a few little issues as well as "tile" my overlays much like the virtual earth image tiles.  That should fix some of my performance problems.

[UPDATE] OOPS! Something I changed last night broke the tracker position.  Not sure where the problem is, but rest assured that I AM at work today, and not still at home.