I would like to copy files between Galaxy S3 and Ubuntu

* without giving away too many privileges - just copying said file
* without any rooty system modifications (I want to keep the carrier-warranty including their system updates - currently 4.1.2; and I want to show this to hapless users too - without them calling me back...)
* without using an USB cable (I know how to do this like in [this answer](https://android.stackexchange.com/a/36958/28620), that is, connecting as a camera ; but this gives one complete rw access in some directories)
* preferably without any extra apps to install.

It seems there are two options left (when going through the list offered by the "Share via" button): either Bluetooth or Wi-Fi.

For Bluetooth such a transfer worked with an out-of-the-box [preinstalled](http://www.ibiblio.org/Dave/Dr-Fun/df9507/df950713.jpg) Windows. So it is not the Android as such which is a problem, rather Ubuntu but [there was no answer nor interest on AU](https://askubuntu.com/questions/240930/sending-pictures-from-android-to-10-04).

When I try to send it via Bluetooth I just get the notification: "Bluetooth share: Sent 0 successful, 1 failed". However, I can transfer files from Ubuntu to Android.

So how can I copy files successfully?