Duplicate Content is the major issue and Google always penalize those website which are fall in this category. If you are thinking that You are not copying other posts so you are safe, you may be wrong. Google has different view in this. You may be penalize for showing your own post on two different URLs.
If you are a wordpress user, you know that you post will be available at its own URL, its category URL and tag URL. If your blog’s Category and Tag URLs are also indexed in Google, you are selected as content farm by Google.
You can read more on: How To Remove WordPress Tags & Categories from Google Search Results?
If your blog is single author blog, your author page and your home page will be similar. In this case, indexing of your author blog will also create a trouble for you.
Now i will talk about showing post excerpt at homepage. I have seen many themes which shows full post at home page. If you are using blogger, you will often get these kinds of themes. Suppose you are using the theme which shows full post at home page. In this case, full content of your post is available in the home page and also in the post page. Same content is at the two different URLs of the blog. This is the thing which is called content farming. Google doesn’t care whether content is copied from the same domain or other domain. If your blog has these issues, you are going to get a Google Panda slap.
Matt Cutts, head of webspam team at Google, also suggest to show only post excerpt at the home page instead of full post. He also explained that if homepage gets regular update, Google Bots will have an idea that this page is not the original blog post and then it will find blog post page.
Tip: You must disallow author page, tag, category URL from search engines. This may cause duplicate content issue.
You can learn more on it from Matt Cutts. See the video below.
I think using a magazie style theme will be better for a blog. It only shows post excerpt with image thumbnail and read more link to post. It also looks nice and reduce the page size.