I'm not sure just walking away is the best advice.
You are legally obligated to pay MF. So, worst possible scenario, they could:
1. Sue you for MF, and get a judgment against you for it
2. Sell the bad debt to collections. Collection agents can harass you, and also, get judgments against you
3. Regardless of whether or not they do any of the above, there's an excellent chance they can put negative accounts on your credit report at the very least. This would stay on your credit rating for at least 7 years.
You may not care about any of any of the above, especially if you are elderly and don't have any need for "credit" anymore and don't plan on making any purchases where a bad credit rating would matter. Just keep in mind, especially if you own a lot of assets, or multiple homes (only your primary residence is protected from creditors), you may be a target for collections...
I'm not saying any of this will happen, but it could. So in that regards, just telling people to damn the consequences and walk away is really bad advice...