I don't think there's anything wrong with "gaming the system", long as it's completely legal. If you can rack up $100,000 in student loan debts, and there's a completely legal way to only pay back $15,000, go for it! How is it different than getting your student loan paid off (or forgiven, or whatever term is used) for doing some civic service? Do X, only have to pay back Y, simple. Yeah, I know that wasn't the point of the article itself (a greatly reduced repayment was nice, but it was due immediately and guy couldn't pay it immediately). But if he'd saved the money required, hopped overseas and paid it off? Fine by me.
As for walking away from a mortgage, it's simply a business transaction. Contracts are broken all the time. That's why there's penalties spelled out in the contract for what would happen. For a mortgage, in some states it's simply that they'll take ownership of the house and kick you out. In other states, you'll be liable for whatever shortfall there is (balance of $100k but house sells for $70k, they can come after you for the $30k difference). The banks definitely went into the deal with eyes wide open, with their teams of lawyers going over everything (and if they're caught unawares, that's their problem). Yes, the homeowner should go into the deal with eyes wide open too, but many don't have a dedicated team of lawyers on their side (at the bare, bare minimum you should read every single word of the contract, no matter how uneasy it makes them feel).
I would view walking away from a mortgage the same as quitting a job one year into a two year contract, and repaying any bonuses that had already been paid (and any other penalties that were outlined in the contract), at least from a moral point of view. Really the same difference. You agreed to do something, and also agreed that if you did NOT do it, then the other side would get some kind of compensation (in the case of a mortgage, a house; in the case of terminating employment early, repaying any bonuses and whatever other penalties). Heck, you can even compare it to breaking a mobile phone contract early; you agreed to stay with Verizon for two years, then decided one year later to switch to T-Mobile; you call Verizon to cancel, and happily pay the ETF. Important business people break contracts all the time and it's no big deal; why is it such a horrible thing when an average person breaks a contract (and only specific contracts at that)?