(13)  Subsequent Events

On November 20, 2012, we executed an amendment for the operating lease of our San Francisco headquarters and extended our lease commitment to early 2019. The additional future minimum rental payments amount to approximately $30.6 million.

On November 16, 2012, we entered into a noncancelable sublease agreement for a portion of our office space in the United Kingdom. Future minimum sublease rental payments amount to approximately $2.8 million, which will offset future minimum rental payments.

On November 1, 2012, a warrant to purchase 404,651 shares of common stock was exercised for cash proceeds of $631,256.