I recently had a break-in through one of my cornerposts, or so it looks like. (It was weaker than everything else because I never repaired them after the wall-boost a few weeks ago). I think that they may have glitched through the corner now that there was no cornerpost - it's also possible that they just rebuilt the section of wall, now that I think about it. I've heard other accusations of wall glitching, so I figured it'd be best to bring it to the attention of the devs.
I'd post some screenshots, but the server seems to have crashed.
EDIT:
I was urged by one of the others to point out that two of us with fairly high exploration failed to see any Vandalism clue from the definitely-claimed cornerpost, even after passing it by a couple of times. It may have just been bad luck against a high stealth (as the actual stealing was done by what I can only assume is an alt, at least in the mind of the perpetrator, since his hearthfire was left literally adjacent to my property - which I assume was to let him teleport to wherever to stash the goods).