I would think having more than one account is akin to web developers having seperate websites by niches and focus areas. Ie if you want folks to bookmark and return visit a recipe site, you'd focus that site on cooking and recipes, not have a category on video games (as an example).
I myself do not have more than one account, but that's because I'm just getting off the ground. It's something I'll seriously consider, though. I have diverse interest areas, and while some might find my travel posts and reviews interesting, they might not have near as much interest in pet toy reviews or wherever my other interests lay.