The Internet advertising market is growing, but DoubleClick ( DCLK) isn't keeping pace.Though all systems are go industrywide -- and Internet bellwether Yahoo! ( YHOO) is blowing past financial estimates -- DoubleClick's earnings disappointment late Thursday is confirming the doubts of its critics and testing the patience of its fans. Part of the bullish case on DoubleClick -- an offline and online marketing services company -- is that pricing will stabilize in its online ad delivery business, which accounts for nearly half its revenue. The stock's proponents also argue that the company is developing and acquiring a suite of marketing services that will make it indispensible to major advertisers. But the company's inability to keep pace with industry growth, as well as the bigger-than-expected negative impact of a recent acquisition, are calling DoubleClick's ability to execute on its plan into question. The setbacks are giving investors an excuse to look instead toward other online advertising plays, such as ValueClick ( VCLK) and aQuantive ( AQNT). The developments in some ways echo the straits of tech titan Nokia ( NOK). The Finnish wireless giant saw its shares slide 10% Friday on news that its sales wouldn't keep up with the booming handset market. On Friday afternoon, DoubleClick's shares were trading at $8.85, down $3.09, or 26%. ValueClick was trading at $11.23, down 31 cents, and aQuantive was down 14 cents to trade at $9.96.