The SpaceX initial public offering on Friday is poised to be the biggest ever — and is generating a lot of buzz. But IPOs can carry dangers for the average investor, according to finance experts. For starters, stocks are often unprofitable in the early period after an IPO, experts said. And buying individual companies — instead of investment funds with a broadly diversified basket of stocks — can make that volatility more acute for unwary investors due to their concentrated positions. There's