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 health information provider WebMD Health Corp. (NASDAQ:WBMD) surged 20% today after its first-quarter update topped Wall Street expectations.

So what: The stock had pulled back sharply in recent months on short-term valuation concerns, but today's better-than-expected Q1 update reignites optimism over WebMD's long-term growth potential. In fact, the company said that monthly traffic to its health network spiked 32% to 174 million unique users, while page views surged 26% to 3.5 billion, giving Wall Street plenty of good vibes over its monetization prospects going forward.

Now what: Management now expects its Q1 adjusted EBITDA to be slightly above the high end of its previously forecast range of $28.5 million-$30.5 million on sales, which should also be higher than its prior view. "The update to our guidance that we are providing today reflects recent improvements in our sales activity compared to our experience in the early weeks of 2014," said CEO David Schlanger. "We are having very positive dialogue with our customers about how WebMD can help address their evolving business needs and we are continuing our investments in new product and service offerings to better serve those needs and realize future growth opportunities."

Of course, when you couple today's big share-price spike with WebMD's still-questionable competitive moat, I'd wait for a much wider margin of safety before buying into that bullishness.