When I first started writing the maps doodle, I thought that an idea like that must already exist. However, googling in that limited time did not really yield any useful results, and so I thought of writing it myself.
With features like drag and drop signs, the site was an advanced version of the 24 hour that I had put in. A little more dissection showed me the simple tricks that achieved the doodling capability.
Speaking about the polylines capability in Google Maps, they are effectively placed as HTML 4 SVG tags on the map. This was the only difference from my design, where I used a canvas to overlay the polylines. A comparison between SVG and canvas is here and here. Apparently, I did not notice any difference in performance with both approaches though.
To conclude, as I have found a service that allows doodling on maps already, I may not continue development of the Maps Doodle. I think I would now start hacking into other stuff !!