I'm not saying NM's guarantors will default or fail, but remember there is always a chance. There's also a chance that NM's book might not fill in 2012. Or it's book might fill but at unfavorable prices. If prices rise while it's locked in to crappy contracts, well, it leads to losses.
There are a lot of risks with NM, so just don't let the $3.50 price fool you. It's $3.50 for a reason. It doesn't mean it can't or won't go lower (or higher)...similar to AIG and/or other concerns that do/have relied on guarantees or insurance.
In fact, your house probably has insurance on it, but if the insurer goes bust, you and/the lender lose. So don't overlook this as a possibility even if chances are remote. This is why I recommend a touch of professional skepticism regardless of the stock or company...at ANY price.