What: Shares of ServiceNow (NYSE:NOW) fell 19% early Thursday after the cloud-based enterprise software company reported better-than-expected fourth-quarter 2015 results but followed with disappointing guidance.

So what: Quarterly revenue rose 44% year over year (51% at constant currency) to $285.7 million, including a 46.7% increase in subscription revenue to $244.7 million and a 31% increase in professional services and "other" revenue to $41 million.

Based on generally accepted accounting principles, which translated to a net loss of $37.4 million, or $0.23 per share, narrowed from a GAAP net loss of $0.30 per share in the same year-ago period. On an adjusted basis, which means excluding items like stock-based compensation, ServiceNow reported net income of $32.6 million, or $0.19 per diluted share, up from non-GAAP net income of $4.9 million, or $0.03 per share in last year's fourth quarter.

Analysts, on average, were modeling adjusted earnings of $0.08 per share on lower revenue of $281.4 million.

ServiceNow's billings rose 33% year over year to (39% at constant currency) to $365.7 million, and the company generated healthy free cash flow of $80.2 million, up 107% year over year.

CEO Frank Slootman added, "We marked a huge milestone in 2015, becoming only the second enterprise SaaS company to surpass $1 billion in revenue. This was our largest quarter yet for net new annualized contract value, punctuated by 26 net new Global 2000 customers in the quarter."

Now what: For the current quarter, ServiceNow anticipates revenue between $298 million and $303 million, including subscription revenue between $261 million and $265 million, and professional services and other revenue between $37 million and $38 million. Overall, that's good for year-over-year growth between 41% and 43% (or between 42% and 44% at constant currency) and above analysts' expectations for revenue of $297.8 million.

However, the market was much less impressed with ServiceNow's full-year outlook, which calls for total billings of $1.6 billion, good for year-over-year growth of 33% to 34% at constant currency. ServiceNow also expects 2016 revenue between $1.34 billion and $1.37 billion, up between 33% and 36% from 2015 as reported and between 34% and 37% at constant currency. That includes subscription revenue between $1.18 billion and $1.20 billion and professional services and other revenue between $160 million and $170 million.

By contrast, analysts' consensus estimates called for full-year revenue near the high end of that range, and it appears Wall Street is concerned that the more modest growth in billings could be a harbinger of greater deceleration in ServiceNow's top-line growth.

At the same time, it's not as though ServiceNow's full-year revenue and billings guidance were overwhelmingly negative. The company is still growing nicely and all the while anticipates demonstrating healthy operating margin and free cash flow margin of 12% and 24%, respectively. But with shares still trading above 60 times next year's estimated non-GAAP earnings, 13 times trailing-12-month sales, and ServiceNow still unprofitable on a GAAP basis, it's no surprise the market is bidding down ServiceNow stock at the first sign of imperfection.