As Twitter's initial public offering opened this week, The New York Times' DealBook reports that Twitter's "biggest potential tax shelter is its history of losing money. Like most growth companies, Twitter has accumulated a lot of operating losses. These losses, in theory, can be carried forward as net operating losses to offset future taxable income. But investors should not count on it." The net operating losses can't be carried forward as Twitter's ownership changes when "founders, venture capitalists and later-stage investors" sell their interests, the NYT reports.