Well, I thought the whole idea is that you DON'T HAVE TO trust the escrow providers.

In the CoinGuard case, it seems that each party will hold some secret to themselves and the escrow provider (E) is only needed if the buyer and seller have a dispute. And the escrow provider cannot take the BTC funds, except to give it to either the buyer or the seller. That's how I understand it works, not sure if the CoinGuard web site explained this clearly.

With regard to the GGDice service, I think it's theoretically possible that the private key is stored on the server, that would be a critical flaw in the scheme, to me anyway.