TiVo, the troubled DVR maker, will soon be on its fourth CFO in less than 18 months. Looks like Steve Sordello, the company's most recent finance chief, has crunched the numbers and found them wanting. He's left for an undisclosed - but "well known" - venture-backed startup. One possibility: LinkedIn, which insiders say plans to hire a CFO this year. Anyone know exactly where Sordello's headed - and what he found wanting about TIVo?