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 Netflix (NASDAQ:NFLX) gained as much as 19% after the leading video streamer listed blockbuster subscriber numbers in its fourth-quarter report.

So what: Netflix tacked on 2.33 million new domestic subscribers in the closing three months of 2013, better than the 2.05 million it added in the year-ago quarter, showing that its already strong growth rate is getting even better. Earnings per share grew more than six times to $0.79 from $0.13 a year ago, beating estimates of $0.66, while revenue of $1.18 billion was essentially in line with expectations. Management guided the current quarter's EPS at $0.78, also matching estimates. The winter months are Netflix's strongest, and the company expects to add another 2.25 million domestic subscribers in the current quarter.

Now what: It's hard to doubt Netflix's dominance in the video-streaming industry. The company pioneered the business model with mail-order DVDs, and it's now successfully navigated the transition to streaming with the biggest library and the greatest subscriber base, bringing a serious threat to premium cable channels such as HBO and Showtime along the way. But while the business is strong, the stock is dearly priced, commanding a forward P/E of 100. Investors may want to consider how long Netflix can grow at this pace before jumping on the bandwagon.