The only individuals responsible for this are the criminals themselves, be they Linode employees or not. Linode has no moral responsibility to refund the victims. However, if they do not they risk gaining a seriously bad reputation forcing others to look for a VPS that assumes responsibility for loss or theft of a client's assets. Like all things, competition will allow for a diversity in quality of services. Some VPS's will be insured against theft, others will not. Some will refund victims, others will not. If Linode chooses not to refund the victims, so be it. If you don't like that about Linode, find a VPS provider that will.
I would be very surprised if any hosting company (VPS or otherwise) will assume responsibility in the form of economical compensation for incidents like this. Every Terms and Conditions I have read from virtually every hosting company I have worked with is very clear about no compensation for damages of any kind, for any reason.
If there is enough of a demand it will happen. Sure, the VPS premiums are likely going to be a lot higher, but it can happen. What we're really talking about here is insurance. If the VPS doesn't supply the optional insurance, then individuals will have to get it themselves. Take Tradehill. They could have gotten some insurance before this situation ever happened. They could have been insured up to, what was it, 45,000 BTC? In the case they got ripped off the insurance would have kicked in, and the insurance provider would have the most interest in catching the criminal and recovering the stolen bitcoins. Now, I'm sure no CORPORATE, "legal" insurance company exists like this right now. But there is definitely a need for one. Wasn't there a poll the other day asking people what is most necessary for Bitcoin? One of the poll answers was "insurance." I didn't participate in the poll, but my answer was "insurance" when I read it. Nobody else picked that one though. Perhaps it's time for a Bitcoin insurance company to pop up, preferably one that is totally underground, i.e. not sanctioned by the government at all.