Google's hcief financial officer George Reyes today said advertising revenue growth could slow, sparking a sell-off of as much as 13 per cent in the Web search leader's volatile stock.
CNBC financial television reported that Mr Reyes, speaking at a Merrill Lynch investor conference in New York, said Web search advertising, which is responsible for 99 per cent of Google sales, would depend on overall market growth or moves into new markets instead of improvements in its ad business.
"Growth is slowing and now largely organic," Mr Reyes was quoted by CNBC financial television as saying. "The search monetisation gains have now been largely realised."
A Google spokesman declined any comment on Mr Reyes' remarks.
Organic growth relies on factors such as overall Internet users or the number of Web search queries, instead of business efforts Google makes, such as modifying its pay-per-click ad system to place more ads on each page.
Google shares dropped as much 13 per cent, or more than $50 in heavy trading, before recovering to trade down $22.37 at around $368 on Nasdaq.
Because Google, unlike most large publicly traded US companies, has a policy of not commenting on its financial targets, its share price has reacted wildly to indications on its performance.
In late January, when Google reported disappointing fourth-quarter earnings, its shares fell as much as 19 per cent.
Google shares started to bounce back today after bullish analysts stepped up to defend the stock. Morgan Stanley, Goldman Sachs and Piper Jaffray analysts, among others, argued that Mr Reyes' comments referred to long-term growth prospects and that investors had overreacted.
Mr Reyes said he believed "a lot" of growth lay ahead, but that the rate of growth was in question, according to a Dow Jones report. "I'm not turning bearish at all," the story quoted Mr Reyes as adding.
Ben Hunt, a buy-side analyst with Iridian Asset Management, who watched the Google presentation, said Mr Reyes introduced doubts at the last minute after an otherwise upbeat speech.
"I thought his comments were bullish until, at the very end, he said that because of 'the law of large numbers,' there is going to be challenges to their revenue growth rate."
Piper Jaffray analyst Safa Rashtchy, who maintains a price target of $600 on Google shares, said Mr Reyes comments had been "misinterpreted" and that the stock is likely to recover following the annual Google Analyst Day on Thursday.
"The CFO's comments that they are going to have to find other ways to monetize the business should be taken positively, as we believe that this indicates that Google will aggressively purse other revenue streams," Rashtchy wrote.