Earlier this week Turntable.fm crossed a milestone. No, it wasn’t hitting a reported 140K users one month after launching, nor was it being added to the list of portfolio companies for First Round Capital (granted it was just a logo refresh from the company's previous product incarnation, StickyBits ). In fact, the ultimate sign that the crowdsourced music service had arrived was more subtle than a milestone metric and ran under the radar for anyone who isn’t finely attuned to these things; on Tuesday the artist Sir Mix A Lot (of “Baby’s Got Back” fame) DJ’d a set on Turntable.fm replete with a custom hacked avatar that differentiated him from the available cookie cutter options.