Theoretically, new A.I. start-ups could compete with the giants over privacy and respect for user autonomy. But investors aren’t holding their breath. “If software is meritocratic, A.I. is feudal,” said Nick Beim, a partner at the venture-capital firm Venrock, which invests in A.I. start-ups. He has found that A.I. is an uphill battle for new entrants into the field, and not just because the technology is complicated. “Its power depends on how much data you have,” he said. “And when it comes to data ownership, the large internet platforms are in a dramatically different league than everyone else.”