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 Millenial Media, (NYSE:MM) plunged more than 14% Thursday after the company turned in disappointing forward guidance.

So what: Adjusted fourth-quarter revenue rose 44% year over year, to $109.5 million, which translated to adjusted net income of $0.08 per share. On a GAAP basis, Millenial Media turned in a net loss of $0.04 per share. By contrast, analysts were looking for a loss of $0.05 per share on sales of $95.62 million.

However, the company also expects total revenue in the current quarter to be in the range of $72 million to $76 million. Analysts, on average, were looking for significantly higher first quarter revenue of $83.25 million. Adjusted EBITDA is also expected to come in at a loss between $5 and $6 million.

Now what: Millennial Media's fourth-quarter results were decent, but there's no denying that our market is a forward-looking machine. With shares currently trading at a lofty 23 times this year's estimated earnings -- and keeping in mind those estimates are likely to fall as analysts have time to fully digest today's news -- I think investors would be wise to simply watch from the sidelines for now.

Steve Symington has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.