The Galaxy S III on Sprint has been seeing a considerable amount of update action in the short time since it's been released. Back on June 29th, the device saw a security update and now, according to Sprint's community website, a second "Google security updates" OTA software patch is headed to the device.
The carrier hasn't offered any details on what the update fixes, beyond that today's update is Google-related, while the previous update is just a generic security update. Still, it's interesting to see that the device has received multiple security updates within less than a month. We haven't heard of any major security issues, so this may just be a bit of proactive protection.