I have my doubts regarding this as well.
For example, a house or organization that has a law along the lines of "unregistered bases found in blablabla will be subject to destruction" should not be required to send a communication informing the owners of their base's imminent destruction. Such a law should be considered sufficient "forum role play" to warrant a siege.
It's rather strange for factions like nomads, too. Sure, they could send a transmission with a shooped image of the base and some ***'we' 'ours' (anger) blablabla***, and although that would be nice roleplay it's kind of silly to warn the owners that their base has been discovered.
I really like the part of the rule that specifies that the attack must make sense in roleplay, which would prevent people from using totally illogical oorp alliances to siege bases, or just randomly attacking bases for no reason.
The forum part though? Meh, not such a great idea.