According to this article, about $1 billion in Independent Foreclosure Review settlement checks remain uncashed. The checks are only valid for 90 days. Checks issued in April have started expiring. If you've received an IFR check, but haven't cashed it, then be sure to cash it before it expires.
While some articles I've read indicate that the uncashed checks may be a form of protest against the entire IFR fiasco, I'm not so sure. More likely is that most of the uncashed checks never made it to the intended recipients. If a homeowner never submitted any paperwork when the IFR was in its earliest stages, then it's highly likely that the only address on file is the address of the foreclosed-upon home. You know, the one that the homeowner left years ago. The odds of that person receiving the check? Slim to none.