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 Marketo (NASDAQ:MKTO) have lost more than 20% of their value today in response to Marketo's publication of its fourth-quarter earnings  report yesterday evening.

So what: Marketo reported strong revenue growth for the fourth quarter, as its $42.3 million top line was 50% higher year-over-year and better than Wall Street's expectations for $41 million. The company's adjusted net loss of $0.18 per share was also narrower than the $0.25 loss per share analysts had expected.

Today's steep drop stems not from these results, but from Marketo's lousy forward guidance. The company is now guiding  its first-quarter revenue into a $45 million to $46 million range, which will result in adjusted losses of $0.20 to $0.22 per share. Marketo also expects its full-year revenue to range from $204 million to $206 million, resulting in adjusted losses of $0.83 to $0.87 per share. Both quarterly and annual revenue ranges top Wall Street's  expectations, but analysts had expected Marketo to lose only $0.16 per share in its first quarter and just $0.63 per share over the full year.

Now what: Marketo is a long way from profitability, and today's drop reflects investors' increasing concern over the company's ongoing hemorrhage of cash. Marketo's free cash flow is still negative  as well, but it has at least been heading in the right direction, in contrast to the deepening shade of red ink on Marketo's income statement. Marketo's executives don't expect to be cash-flow positive  until 2016, so the company's shares may very well continue their slide. I'd watch this one from the sidelines for the time being.