I would think that the time you submit your articles to social networking sites would be the judge of how much traffic you get from them. I would think that you would want to get your new article posted to them right before "peak" blog-reading hours so that they sit fat, dumb, and happy on top vs. being kind of buried by more recently submitted articles. I'm currently researching "peak" blog-reading hours myself so when I find them I'll share
Given that most people get traffic via search engine probably not. But for a few years I've noticed that all of my sites get the highest traffic around 3 p.m. EST so I set entries to go live about then. Richard