Return of Earnest Money justified?

[DW Watson]

I'm selling a house and have the house under contract. Buyer agent contacted me yesterday to let me know buyers decided to terminate the contract with no reasons provided. Isn't this a breach of contract on the buyer's part? Buyer wants earnest money released and has sent me a form to sign for the release. Are the buyers entitled to receive their earnest money back if they are the ones who choose to cancel the sale? (After further investigation I learned the buyers were afraid rental income from the property would not meet their expectations.) I know buyers have a right to terminate the contract if they choose, but isn't the earnest money considered just compensation to the seller for the breach of contract?