How far can the euphoria over Alibaba Group Holding Ltd. go? Even by the standards of online retail, its rise has been extraordinary. Revenue has grown by an average 52 percent annually over the past five years. Its 158 billion yuan ($23 billion) of sales in the 12 months through March was more than 10 times the 2011 figure. Far from slowing down as it grows, Alibaba appears to be keeping up the pace: Revenue will increase 45 percent to 49 percent in its 2018 fiscal year, the company said at its investor day Thursday.