Comment 3 for bug 1374343

To summarize:

 * It's better to have a folder that is writable by all users. But for systems where there is only one user (like most personal usage) I think this is not a "must". On systems with many uses it's nice to have. I think we can have a look if this can have some security issues (it it does have we must ask us again if we really need a folder writable by all users).

 * It's a good ideea to have it as tmpfs. This way a reboot will clear everything ... just in case. If not we can always make a workaround.

* $XDG_RUNTIME_DIR it user related. So it we need a "global" place I don't thik this is the right place. But if we need an env variable we can pass it to crontab job.

I think that we should to the following actions in this order:

 1. Find if we really need a folder writable by all user ? What are the pro / con ? What can be the disavantages of using a "per user" folder ?

 2. We should implement a flexible approach. To find the right folder by searching in this order
     * Check a global property from the settings
     * Checking a env variable (ex: BIT_TMP_FOLDER)
     * Using an evn variable ($TMP, $TEMP, $XDG_RUNTIME_DIR)
     * Use /tmp

What do you thing ?