I think no, having more accounts won't bring more money just because the content has to be original. Instead - concentrating on only one account makes the writer look more professional as he becomes more and more involved in community. Working more on the second account - people would work less on their first one. There fore - instead of having a great account and building good relations in community - they will have two average accounts, not much notable. That is why, I guess there is no sense to have 2 accounts for HP.
With blogging - the story can be different - if you write on different topics, you might want to have a separate blog for each particular niche you're writing for. This way - if you're writing about the history of ancient languages (one of my favorite topics :) ) and butterflies - people who subscribed to your blog because of beautiful little flying creatures won't be bored with descriptions of ancient Chinese characters of Han dynasty (again - my favorite dynasty :) ). Thus you will have more targeted readers who will stay with your blogs longer as they would know what to expect.