As many of us know he seems slightly unhinged now, his recent spat with me where he refused to allow the community to decide a very simplistic bet. Recently there have been more and more issues with his escrow clients (the most recent one, where he returned the escrow payment to an address the user didn't control..).
His personality put aside, there are multiple risks associated with a single holder of funds. Even DNM's have moved to multisig, so why is Theymos letting OG keep so many BTC? You only need to look @ CET escrow service who are holding funds for an ICO with far more than the forums funds, they are a group of people spread half way across the globe with multiple keys held by multiple people.
Personally, I believe that OGNasty is not the man he once was - with his Fanclub seats falling in price quicker than a suicide jumper off a bridge, should the forum still trust this man?
Edit - OG sees Multisig as complicated... shame the Dinosaur isnt keeping up with the times.