You have to install an app to transfer files between a Mac and Android 3.0
Up until recently transferring files between a computer and an Android phone or tablet couldn’t be much easier. You just plugged in a USB cable, and selected “Turn on USB storage” on your Android device and suddenly your phone’s SD card popped up as a mass storage device on your Mac, Linux, or Windows computer. But Android 3.0 does things differently.
If you’re using a Mac running OS X 10.5 or later, you’ll need to download and install Android File Transfer to copy files to and from your phone or tablet. The first time you connect your Android device, you’ll need to double-click the File Transfer app to open it, but after that the process will be automatic.
If you’re using a Windows computer you don’t need any special software. And if you’re using Android 2.x, you can pretty much ignore the Android File Transfer utility as well.
The web site doesn’t mention Linux, but I’d be surprised if you needed to install anything to transfer data between an Android 3.0 device and a Linux machine.