I hate using a 3rd party website for the escrow and in that case rather use someone known. But yes, got alternative.
The double-deposit placed in escrow. If the person who receives the hardware does not release the funds (once he found the hardware is working) he'll use his half of the deposit.
The way a two-party double-deposit escrow with a smart contract works is like this.
You are buying an old miner from me for 1 BTC. I create the smart contract and the first key of a joint multi-sig account in Halo and send you the contract including the public-key of the wallet created. You then create the 2nd private-key on your end, add my public key and send me your public key which I import to link up our joint account.
We now have a joint account and a pending smart contract. I then deposit my own security of 1 BTC to the address and you'd have to deposit 2 BTC (buying price and security) to the same address and the smart contract is updated and locks in the funds. Now you can't access them and I can't because we're on a joint multi-sig account with a timelock defined in the smart contract.
I then ship you the miner and send you the shipping details and the contract is updated as shipped. For the escrow this means that 1 BTC of your 2 BTC is now moved to my end of the agreement and you're still tied into it for your 1 BTC security.
You then receive the miner, test it and if you find it working you'll update the contract stating that the deal is complete. I will counter-sign and your 1 BTC security is released to you while I'll receive my security back and your 1 BTC at the same time. Contract complete.
Now, let's assumed the miner is broken, does not work etc.
If I was to not solve the problem with you then there is no way I as the seller would get my security back let alone your 1 BTC for the purchase. It makes trying to scam you irrational because at that point I'm 2 BTC into it and you're 1. It's only in my interest to resolve the problem with you so that I can get my funds or reverse the sale to get my deposit back.
For you on the other hand there is no reason to bullshit me about the miner working or not. Since the funds are tied up I would have to offer you to ship it back and if you don't then you end up still having 1 BTC tied up in escrow that you can't get too.
See where I'm getting at? The way a double-deposit escrow with a joint account works leaves very little room to be exploited or in fact none because each party will simply lose their funds and scammers don't want that.
Obviously a P2P transaction between to people exchanging BTC for Fiat is less complicated than physical goods. If I sell some BTC for Skrill for example then it's a very simple procedure since receiving the Skrill payment only takes a few minutes and those can't be reversed. In that case it really just takes a quick smart contract setup, double deposit by the buyer and I hedge with a small amount as security, he sends me the Skrill and I counter-sign the contract to release the funds. If I don't, I'll lose my own security which equals the amount the buyer send me via Skrill. So I'd come out with 0 which makes no sense 
I agree three.
Nothing wrong with discussions of cloud mining services and payouts and everything that comes with it but the sale of the accounts or shares or contracts shouldn't be allowed. During my time as Moderator on HT I've seen so many people getting scammed and approached via chat that it was sick. In the first weeks or even month of the new HT on nodebb so many folks got scammed. It was sickening.
