It's not too far off that there will be a small hand full of currencies that will be used across games \ platforms that you will be able to use to make real world purchases. Eventually there will be a "hub war" between tech companies I.E. Google vs. Facebook. The closer we get to being hardwired to the web 24/7 the more relevant this stuff will become. The IRS has already made attempts at taxing game currencies, the only reason they backed off is because it's going to be a giant pile of dicks when they do it.
The operation I'm partnered with in SL has skyrocketed over the past couple months. I had a couple meetings this week with some of SL's lower management in promotions and I start training with them next month. They have an annual Sci-Fi convention where all these independent creators set up their booths and display their new avatars, skins, gear, buildings, vehicles.....basically anything you can imagine.
All open source, 0 subscription fee.