Facebook still doesn’t know how to make money. That was the main conclusion to be drawn from last night’s BBC presentation Mark Zuckerberg: Inside Facebook. When it overcame its excitement at being granted an interview with the founder, the programme offered a few choice insights into how Facebook is still miles away from solving the puzzle of how to generate substantial advertising income without enraging punters who thought they were signing up for a cuddly website free of vulgar commercial messages.