Here's a one liner similar to Flambinos:

(people1 + people2).group_by {|x| x[:name]}.values.select {|x| x.size > 1}

Here's a one liner similar to Flambinos, but in my version, rather than mapping, producing unwanted nils, then compacting them, you are simply selecting the elements that you want. The intent is more transparent. It also allows you to use blocks with one argument only. These are subtle benefits, to be sure, and I like Flambino's solution, but I thought the improvement was worth posting

(people1 + people2).group_by {|x| x[:name]}.values.select {|x| x.size > 1}