Cityfile encountered a stubborn mystery this week: Why did Huffington Post co-founder Ken Lerer help People magazine reporter Joey Bartolomeo buy a $1 million Upper East Side apartment? Bartolomeo and Lerer were mum, but we've found a (mundane!) answer.

Many people have criticized The Huffington Post for not paying its writers. But Ken Lerer, who co-founded the site with Arianna Huffington and remains the company's chairman, sure has one heck of a generous streak. Last week, we noticed that Joey Bartolomeo, a senior writer at People and frequent TV talking head,…