When a web page includes the script console.log("Hello world!"); ... the message is logged to the JavaScript console, but not the Web Inspector console. Using XCode, it doesn't appear that WebCore::Console::log is being called. Instead, it appears that the call is being dispatched to some objective C function via ObjcInstance::invokeMethod (line 186 in objc_instance.mm), but we weren't able to step into the invocation using XCode.
Created attachment 18383 [details] Example page that calls console.log("Hello world!")
Thanks for the bug report, but this is actually a bug in the Safari application. If you feel so inclined, you can file it at bugreport.apple.com.
I've submitted a bug report to bugreport.apple.com: <rdar://problem/5682932>