Today I filed a flight plan but forgot to input an alternate destination.
The flight plan was send without asking for an alternate (it is mandatory to have at least one alternate)
So the flight made its way to some destinations (Italy) but not others (Switzerland), some confusion was created.
Luckily I noticed my error, canceled the original flight plan and filed a new one.
I think it would be a good idea to be asked for an alternate before the flight plan is sent.

To go a step further, I wonder if a notification (email/SMS) would be possible in case a flight is refused or amended by ATC.