I see a few places that this is used in the ow_static but not alot of use outside of that. From what i have read so far its suppose to make finding js errors easier.  

http://stackoverflow.com/questions/1335851/what-does-use-strict-do-in-javascript-and-what-is-the-reasoning-behind-it

The core devs im sure know about this but just in case can you pass it along, it makes for a good read :)

thanks