I've yet to see someone stake such an official claim to an area in the game that they actively try to chase other players off.
I only wish I could say the same thing, Rage.
Let 'em try to chase someone off. That's what filing griefing reports are for; it isn't like they can actually
do something to force someone out, unless it's opposing factions who are flagged and have an ability to enforce (or attempt to) their desires. :)
It again comes down to respect; if you come into an area that you've claimed IC, and you see someone else doing something there, you just let them be. If they're RPing but have no current ongoing stories with your RP crew who's "claimed" the area, you just be polite and leave til they're done. If they're involved in RP with you otherwise, you may have good reason to initiate some RP to find out why they're there.
It's typically why RP that isn't facilitate by actual game mechanics (like cross-faction fighting via PvP flagging) should usually be worked out ahead of time. If it isn't, you have people standing there blustering at each other with no real ability to take the RP anywhere. Inevitably, someone winds up having to godmode their way out of things just so they can keep doing what they were there to do, which doesn't work well for anyone.
Communication and respect. We're all one large RP community who should make every effort to be friendly OOC so we all have people to RP with IC. Ragefang might not be terribly fond of most Hordies (at least those who aren't Death Knights...) IC, but OOC I've only met two or three players who I wouldn't want anything to do with when I poke my head out of the sand Horde-side. The rest I'm happy to play the game with. :)