Best thing to do would be for Linode to generously reimburse these people, but they have no obligation to do so.

As a policy, it would neither be good business nor appropriate for Linode to assume all of the risk in a situation like this.

Also, if Linode did put a policy in place to assume some of the risk (some sort of insurance policy) they open themselves up to scams (just get your friend to rob your bitcoins and cash in on Linode's good will insurance policy).