Update: It looks like in order to fix one thing, you have to break something else. Reports are pouring in that this update breaks Wi-Fi and USB-tethering. Stay tuned for more details.
Owners of the Nexus S have been plagued by a notorious bug that activates Voice Search at random times, causing some serious interference when trying to accomplish even the most simple of tasks. Fortunately, El Goog has stepped up to the plate and addressed the issue, as an OTA update is currently rolling out that will put a stop to this annoying quirk.
The fix should be hitting devices all over the US and Canada, so keep an eye out for it to land on your device shortly.