USA Today: Shares of search engine company Yahoo plunged more than 7% on Tuesday after an IRS official told a group of corporate lawyers at a luncheon in Washington that the government agency is reconsidering a rule related to corporate spin-offs that could complicate or delay Yahoo’s planned spin-off of its massive stake in online retailer Alibaba.Yahoo has been planning to spin off its stake in Chinese e-commerce giant Alibaba into a new company later this year.