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: The theater went dark this morning as RealD (NYSE: RLD) shares fell 12% in trading.

So what: Today, 3-D technology company RealD wasn't as exciting after a disappointing 3-D box office this weekend. BTIG analyst Rich Greenfield said only 36% of theater attendance this weekend was at 3-D movies, worse than last year.

Now what: We may be sorting out the point when we've saturated the market with everything 3-D. Consumers just aren't willing to pay extra money to bring the kids to Kung Fu Panda 2 in 3-D when the "wow" factor isn't there. Box office hits like Avatar will continue to be in demand in 3-D but not every movie fits that bill.

Today's move shows the real difference between RealD and premium 2-D or 3-D operator IMAX (NYSE: IMAX), which is up today. I have made IMAX my top stock pick for 2011 partly because it can benefit no matter whether 3-D catches fire or not. I still like RealD's business, but the stock may have gotten ahead of itself for now.

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