Yahoo! ( YHOO) just got a good look at the hazards of providing accurate guidance to Wall Street. Just one quarter after the Sunnyvale, Calif., Net media giant ignited a wild rally by outshining the most bullish forecasts , investors this week were rubbing their hands together in anticipation of a repeat performance. The problem, it seems, is that Yahoo! responded to its first-quarter surprise by supplying forecasts it deemed more realistic. Thus, when the company posted results late Wednesday that were strong by any normal yardstick -- revenue up 90%, earnings double the year-ago -- investors pummeled Yahoo! for snubbing their guidance-beating ritual. Wall Street steadily regained its wits throughout Thursday's session, as Yahoo! shares retook some of the ground they lost in a postclose Wednesday drubbing. After dropping as much as 11% Thursday morning, Yahoo! shares closed lower by $2.52, to $30.08, a decline of 7.7%. Following a huge run-up in recent months, Yahoo!'s shares hit a 52-week high of $36.51 last week. "We had a record quarter," Yahoo! CFO Sue Decker told TheStreet.com Wednesday evening. "We were really pleased with the results." The significant growth in advertising in the first quarter -- sponsored search in particular -- "took everybody by surprise," she said. "We incorporated that very strong growth and the much-higher base base into the outlook for the rest of the year and gave a very realistic outlook." A little too realistic, apparently. It did no good that Yahoo!, reporting revenue of $609 million, came in at the high end of its guidance range of $580 million to $615 million. (Those shorthand revenue numbers exclude traffic acquisition costs for the company's Overture Services paid-search unit.) It also did no good that the marketing services business -- which now comprises more than three-quarters of Yahoo!'s net revenue -- grew 45% year-over-year on an organic basis, compared with 47%-48% in the first quarter. Sure, the second-quarter number is lower than the first, but it appears to be ahead of industrywide online advertising growth. That implies, according to Yahoo! CEO Terry Semel, that Yahoo! is taking share.