Sometimes, it's just nice to see things from a visual standpoint. Check out this post where the author put together a graph that visually shows how both XM and SIRIUS have progressed in gaining their subscribers. This is based on official subscriber numbers and not any estimations.
Note the bump in SIRIUS' graph in 2005. It's interesting to see how the curve changed the way it did. Also note the rapid angel of growth - anyone still doubt that this technology doesn't have potential?

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