Gmail recently changed the "Attach..." button with a flash one. Today I found out why. Now one can attach multiple documents with one click. It's awesome.
Update: due to some comments here are some screenshots:
On a mac (firefox) it's working:
On Windows (firefox) there was no flash button. (I've seen Gmail and other google applications change the look&feel on different browsers and different google users. Maybe that's the reason.)
The screenshot:
