What's a Handshake Worth Today?

In the really really old days, people shook hands and the deal was done.  I recently had a 3 tier deal that turned into a disaster for multiple seller/buyers, because the first tier was based mainly on a handshake.  Yes all the approved real estate commission forms were signed as required, but between the buyer and the seller, the handshake was the important part of the deal.  This was to be a cash deal where my buyers ran into roadblock after roadblock in providing me with Proof of Funds.  Well the deal progressed and the seller of this property was not too concerned about the lack of Proof of Funds, as he was a firm believer that a handshake made the deal.  He trusted the would be buyer explicitly.  Those sellers of this property went under contract on a purchase of another home, and those sellers went under contract on the sale and purchase of another home, and so on and so one.  Long story short.......my buyers could not perform in the end and everyone's deals went south and alot of earnest money got forfeited.  Lesson learned.........don't EVER proceed with a cash offer unless you have Proof of Funds, no matter what story is.  Oh, and even though much earnest money was lost by the would be seller of my deal, that isn't what hurt him the most.......it was the handshake.