Focus stealing (dialogs or program windows appearing in the foreground while the user is working in another window) is bad:

• If the user is typing while the new window appears, it is very likely that the new window will receive unwanted input. The consequences reach from harmless things like writing some letters where they do not belong to, to fatal errors like inadvertently triggering a reboot or accepting the deletion of files.
• Windows popping up while the user is working on something will distract them, causing major annoyance and disturbing their workflow.

Once there was a Registry setting to prevent programs from doing this, but this setting does not work anymore since Windows 7.

There is no workaround for this (except for not using any program that steals focus, which is practically impossible) - but even if there was, this is not the users fault, and it is not their responsibility to fix this. Focus stealing also happens in Mac OS, but there at least hitting a key on the keyboard does never press a button in a system dialog.

This can only be efficiently fixed at the level of the Operating System.

There are some articles and forum posts regarding this problem, but no comment at all by Microsoft, Apple, Canonical or any other OS creator, thus I launched this petition to make them be aware of this!

Links:
https://en.wikipedia.org/wiki/Focus_stealing#Microsoft_Windows
https://blog.codinghorror.com/please-dont-steal-my-focus/
http://useful-sounds.de/pivot/entry.php?id=102
http://radio-weblogs.com/0103807/stories/2002/06/07/dontStealMyFocus.html