Smoking out leads in cyberspace isn't the gold mine it used to be.

QuinStreet's (Nasdaq: QNST) shareholders are feeling the pain today, after the Web-savvy provider of vetted leads warned of near-term weakness.

QuinStreet is eyeing flat year-over-year revenue growth for the current and upcoming quarters. Analysts were banking on top-line growth of 16% and 12%, respectively. QuinStreet's outlook also calls for revenue of $455 million to $475 million for the new fiscal year, which kicks off next month. Wall Street was targeting nearly $480 million.

QuinStreet is usually a well-oiled machine. Unlike Google (Nasdaq: GOOG) and Microsoft's (Nasdaq: MSFT) Bing that simply let advertisers bid on keywords in search engine queries, QuinStreet operates narrow vertical content sites in niche areas including financial services and for-profit post-secondary schools. By engaging visitors, QuinStreet is able to deliver more qualified leads to advertisers that are willing to pay more for vetted referrals. QuinStreet's sales pitch to advertisers is that its hands-on approach delivers greater sale by shaving as much as two-thirds of customer acquisition costs.

There have been hiccups along the way, but largely on the end of its areas of specialty. Serving up leads to home service providers or online universities isn't as lucrative as it was a few years ago. DeVry (NYSE: DV), for example, accounted for nearly a fifth of QuinStreet's revenue two years ago before scaling back.

QuinStreet's deep dives place it in a more compelling position than performance-based peers including Marchex (Nasdaq: MCHX) and ValueClick (Nasdaq: VCLK), but the market's never exactly seen it that way.

There wasn't a lot of buzz when QuinStreet went public last year. It was priced at $15, opened at $15, and closed its first day of trading at $15. Obviously, the stock went on to trade in a much wider range, but it was already trading as a busted IPO before last night's news.

QuinStreet isn't broken. The midpoint of its top-line range for fiscal 2012 implies a growth rate of 15%. QuinStreet's guidance calls for adjusted EBITDA margins to clock in at a reasonable 20%. If anything, today's pummeling may be just enough to ring the dinner bell for potential acquirers. QuinStreet's model works. Its areas of marketing specialty just happen to be somewhat out of favor at the moment.

I wonder if there's a deep vertical content site out there to smoke out acquirers for busted dot-com IPOs?

Is online advertising in general vulnerable these days? Share your thoughts in the comment box below.

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Longtime Fool contributor Rick Munarriz considers himself a vetted lead. He does not own shares in any of the stocks in this story. Rick is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early.