I think the idea is rather pointless, due to the amount of resources 
needed (you have tens of millions of square kilometers to paint!) and the 
very likely backlash from irate people the world over. Just remember the 
uproar over the space billboard a few years back from astronomers and the 
public. Besides, it is hard to change the advertisement.
My suggestion is that you invest in enhanced reality advertising instead.
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Anders Sandberg                                      Towards Ascension!
nv91-asa@nada.kth.se         http://www.nada.kth.se/~nv91-asa/main.html
GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y