I'm just thinking out loud here, but I would suspect that the IRS would only know that the debt was forgiven if the debt owner wrote the debt off as a loss on their taxes. If they simply hold it and do nothing, even if they deleted it from your credit record (which they can do), no taxable event would have occurred. I could be wrong in this crazy country of ours, but I believe there is no law requiring a debt owner to attempt to collect on it, or to write off a debt as noncollectable after a certain period of time.
I'm not 100% sure, but I'd be completely shocked if the banks and credit card companies (or whoever) that sell the debt didn't have to report the sale to some government agency, or even the IRS itself, so the IRS could probably find out that way.
And now that OWS has announced they're buying up debt and forgiving it, the IRS is going to have a pretty good idea what's going on...
