Good intentions aside, I've kinda tended to think it's a bad idea---not simply for any potential tax liabilities that might accrue to the debt forgivers---but also because it's transferring risk from the legally assignable parties (banks/collection agencies) onto the shoulders of people who bear no responsibility for the debt in the first place. Put another way: any financial institution that is willing to sell you someone's indebtedness for only five cents on the dollar obviously has little if any hope of retrieving any of that debt. So why bail them out? That's essentially what Occupy is doing, and while I can see the moral case to be made for this, you really can't see this buyback initiative accomplishing much more beyond extracting a few drops of water from a very big bucket. There's just no way to scale up a voluntary initiative to the funding levels needed (i.e., trillions of dollars) to have any meaningful impact on our various debt crises (housing, medical bills, student loans).
A more effective alternative strategy, to my mind, would be a series of organized rent strikes, in which large pools of people---millions, ideally---simply refuse to make their mortgage or student loan payments at the same time. The goal, of course, would be to starve the financial system into submitting to customer demand to renegotiate the terms of home-loan and student-loan debt, and as an act of mass civil disobedience, it seems to me like a good fit for people who cut their teeth on organizing sit-down strikes. Either way, though, using your money to buy up uncollectible debt seems like a poor use of resources, and it tends to incentivize bad behavior by lenders; why should they ever write down debt of any kind when they know that some sucker will eventually be wiling to take it off of their hands?
---Baron V