13. A system comprising: a server system including one or more machine-readable storage devices that are programmed with instructions that, when executed by one or more programmable processors, obtain information that identifies a level of inclusion of a particular word in queries that were received over a defined recent period of time; an updater, embodied in one or more machine-readable storage devices that are programmed with instructions that, when executed by one or more programmable processors, modify a speech recognition model to revise occurrence data for the particular word based on the level of inclusion of the particular word in the queries that were received over the defined recent period of time, wherein inclusion of the particular word in the queries that were received over the defined recent period of time influences the occurrence data more strongly than does inclusion of the particular word in queries that were received over time outside of the defined recent period of time and before the defined recent period of time; and a speech recognition system, embodied in one or more machine-readable storage devices that are programmed with instructions that, when executed by one or more programmable processors: (i) receive a verbal query, (ii) translate, using the modified speech recognition model, the verbal query into a textual query, wherein the textual query includes the particular word, and (iii) determine whether the textual query represents a verbal search query or whether the textual query represents a verbal system command.
13. A system comprising: a server system including one or more machine-readable storage devices that are programmed with instructions that, when executed by one or more programmable processors, obtain information that identifies a level of inclusion of a particular word in queries that were received over a defined recent period of time; an updater, embodied in one or more machine-readable storage devices that are programmed with instructions that, when executed by one or more programmable processors, modify a speech recognition model to revise occurrence data for the particular word based on the level of inclusion of the particular word in the queries that were received over the defined recent period of time, wherein inclusion of the particular word in the queries that were received over the defined recent period of time influences the occurrence data more strongly than does inclusion of the particular word in queries that were received over time outside of the defined recent period of time and before the defined recent period of time; and a speech recognition system, embodied in one or more machine-readable storage devices that are programmed with instructions that, when executed by one or more programmable processors: (i) receive a verbal query, (ii) translate, using the modified speech recognition model, the verbal query into a textual query, wherein the textual query includes the particular word, and (iii) determine whether the textual query represents a verbal search query or whether the textual query represents a verbal system command. 14. The system of claim 13 , wherein the updater is stored on a mobile computing device.