What i can tell about why i like Pobs is that they make room for Fraction interactions and as some Pobs show they are a very good place to get in talking with other players.
So they are a core product of our Offical Fractions out there, what means also a reason for good and much RP.
In my eyes @Czechmate idea about a wall for High core base's (what means that someone really put time and effort in it) with a real use is something to start with.
Also the current Siege system should be reworked to something more reasonable, not just like ''this one has to die'' because someone sleeped bad.