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: Oil prices have been crushed once again on Monday with WTI crude oil falling over 4.3% to $50.44 per barrel and Brent crude price dropping 5.4% to $53.35 per barrel. For a short time, WTI crude fell below $50 per barrel, a price we haven't seen since April 2009 when the U.S. was in the depths of recession. 

So what: Monday's move is driven by a few macro factors that have traders concerned. Fighting in Libya and the bombing of an oil tanker was expected to have a negative impact on oil supply, but increased supply in Russia and Iraq appear to be making up for the losses, which seem to be temporary.

An election in Greece is getting tensions and there's renewed concerns the country will leave the eurozone, a move that could put Europe's central bank and its member countries in peril. That's a big reason the euro is down in trading Monday and the dollar is up. Since oil is priced in dollars the drop in oil prices is only magnified. 

Now what: The reaction in oil prices can be swift and companies are having to respond to a new low in oil prices. Baker Hughes released a count of U.S. rotary drilling rigs in operation today and the results showed active rigs down 29 from a week ago to 1,811 rigs. Since mid-November, the rig count is down 6%. 

In Canada, the rig count was down 19% in the last week to just 208 rigs. Both countries are targets of OPEC, which is keeping the market oversupplied in an effort to squeeze out marginal oil producers.

One area I would stay out of right now is U.S. shale oil producers like Continental Resources (NYSE:CLR) and Whiting Petroleum (NYSE:WLL), which are two of the largest operators in North Dakota's shale plays. These companies will feel the most pressure from low oil prices because they have higher production costs than conventional wells and don't have well-diversified businesses like big oil companies. They need a big recovery in oil just to make it through 2015 and right now that's not on the horizon.