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 Gigamon (NYSE:GIMO) plunged more than 17% during intraday trading Tuesday after the network traffic visibility specialist beat analysts' estimates with its third quarter results, but later issued weak forward earnings guidance.

So what: Quarterly revenue rose 52% year over year to $39 million, which translated to adjusted net income of $5.8 million, or $0.18 per diluted share. Both numbers exceeded analysts' expectations, which called for adjusted earnings of just $0.15 per share on sales $38.34 million.

However, management also stated on Gigamon's subsequent earnings conference call that they expect fourth-quarter revenue of $40.5 million to $42.5 million, with adjusted earnings per share of $0.10 to $0.12. While analysts had expected sales at the low end of Gigamon's expected range, they were looking for higher adjusted earnings of $0.14 per share.

Now what: It doesn't help that Gigamon also recently announced a massive follow-on offering of 5.1 million shares at $38.50 per share, which included 300,000 shares from Gigamon itself and 4.8 million shares from selling stockholders. Of course, that was a not-so-subtle attempt to take advantage of the stock's nearly 40% run-up since the company went public at $19 per share in June.

As it stands, with the stock currently trading at an expensive 68 times next year's estimated earnings (even after today's plunge), its hard to blame investors for following suit.

Fool contributor Steve Symington owns shares of Apple. The Motley Fool recommends and owns shares of Apple. Try any of our Foolish newsletter services free for 30 days. We Fools don't 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.