YouTube is not only grabbing an ever-larger online audience. It's also attracting first-string Silicon Valley executives.The video-sharing Web site, founded just 19 months ago, has hired Yahoo! ( YHOO) Treasurer Gideon Yu as its chief financial officer, according to a report Saturday in The Wall Street Journal. The hiring shows YouTube is maturing and might begin pursuing deals or an IPO, the report noted. YouTube's users now watch more than 100 million videos a day, making the start-up competitive in the online video arena against Internet goliaths like Google ( GOOG). This isn't the first time YouTube has snatched an executive from Yahoo!, the report noted. Earlier this year, it hired Tony Nethercutt to build its ad sales team.