Comment 18 for bug 328575

an added problem with su - is that programs can't communicate. For example login as "work" and su - test -c thunderbird results in tbird not being able to run the browser in response to a click on an url.

This is possible with su thunderbird.

This would seem to be another arguement for passing the session rather than dumping the inaccessible one and auto creating a new one.

My gut feeling is that there will be many such issues spouting from this well if it is implemented with hacky workarounds, as commented in #10 and #17