At around the beginning of this year's Google I/O event, Google had revealed that they've about 400,000 Android activations daily.
Today, just 2 hours back, Andy Rubin, Google Android boss has tweeted the latest Android activation numbers -- according ot Rubin's tweets Android now has 500,00 daily activation:
There are now 500,000 Android devices activated every day, and it's growing at 4.4% w/w.
Just a couple weeks ago, Android's market share dipped for the first time since 2009 according to IDC. However, that had a lot to do with Verizon's iPhone 4 and less to do with a drop in Android sales.