Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Genworth Financial (NYSE: GNW) closed down more than 16% after falling as much as 22% earlier in the trading session. The wealth manager took a beating after being mentioned in a report cited by Barron’s that identified a handful of stocks with major U.S, debt exposure.

So what: Sandler O’Neill + Partners named five life insurers with major U.S. debt exposure, including Genworth, which could see lower book value as the value of its Treasury holdings decline. Others named in the report included Aflac (NYSE: AFL) and Prudential Financial (NYSE: PRU).

Now what: It's far too early to know the implications of the downgrade on book values, but Sandler said declines could come, and if they do, the corresponding stocks would take a hit. Genworth seems to be falling in anticipation of exactly that. Is the haircut deserved, or are you buying at these levels? Weigh in using the comments box below.

Interested in more info on Genworth Financial? Add it to your watchlist .