From an outsiders perspective, I have neither owned a POB or participated in a seige.
I have, however, seen at least one POB destruction message every 3rd time I log on. The frequency at which these things are being trounced is slightly concerning, considering how much time and energy they take to construct and maintain.
Honestly, this whole thing feels like Platinum Miners vs. 20-Mil-R-Dai Pirates all over again. Except THIS time the player being extorted cannot escape and are being held hostage.
If your faction is known for being brutal, ok. Fine. I get a certain extent of brutality exists in-RP. However, ooRP being an excessive jerk because "my faction is a bunch of a-holes" is biting the hand that feeds. And we've seen where this mentality eventually leads. Just ask the Phantoms.
Blow up enough POBs in your ZOI enough times with minimal RP excuses, and players simply won't build bases in your region anymore. They will find more friendly areas and re-build there, assuming they don't ragequit first. Congrats, you just killed an active region and/or decreased the server population.
I don't want POBs to be invincible. They should be vulnerable. They should encourage RP. But using RP to cover up greifing? That needs to stop.