So I just started running blogs in the past few weeks and I've noticed within the first 3-5 days of each site being up all of the posts are indexed in google immediately. 6-8 days the number of posts indexed goes down, and then eventually i'm getting almost zero traffic to them and only 1/5th the number of posts are indexted. I'm assuming this is an issue of duplicate content where as these posts are being made automatically via RSS.... Is it safe to assume that???
I stick to this rule. Never submit site to "top blog ranking sites" with RSS feed. If someone else added your "feed" to blog aggregator, ask him to remove it, otherwise report duplicate content, using Google Webmaster Tools.