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 JPMorgan & Chase sank as low as 10% on Friday after the banking giant disclosed a massive $2 billion trading loss at a London trading unit. So what: In addition to the huge financial hit, the news deals a significant blow to JPMorgan’s reputation: It had come out of the mortgage crisis as one of the relatively healthy big banks. The news is even reigniting worries about the possibility of big losses at other banks like Morgan Stanley and Goldman Sachs, both of which are also down significantly today. Now what: For the current quarter, JPMorgan said it now expects to take a loss of $800 million in its corporate and private equity segment (versus its previous view of a $200 million profit), which will naturally weigh on overall earnings. “We will admit it, we will learn from it, we will fix it, and we will move on,” CEO Jamie Dimon said in a conference call with analysts. Of course, given the possibility of even further losses as management tries to unload the position, don’t expect Mr. Market to move on quite as quickly. Interested in more info onJPMorgan?Add it to your watchlist.