I made a positive decision not to set my blog feed to the short version when I started blogging as I know that people like to read through email/google reader instead of being forced to come to the blog to read the whole post. I'm not driven by page views, so I didn't mind that at all - I'm happy that someone wants to read what I write, however they read it.
Unfortunately, I had to set my blog feed to short when I discovered it was being used to populate some spam blogs (splogs). Not only is it annoying to see your content stolen, if you use the Blogger platform, it can lead to your own blog being marked as a spam blog and frozen (Blogger searches for identical content on blogs as a way of identifying splogs). This happened to www.modestybrown.com only last week, and although she had access restored quickly I don't think she'll mind me telling you that she had a very unpleasant and panicky hour or so until it was resolved.
I found my content being republished by chance as a result of searching for a small brand I'd reviewed, but you can check for unusual uses through Feedburner (if this is how you are publishing your site feed). Click on the 'see and manage more uncommon uses>>' link in feedburner to see where your content is being republished. Most of them will be through things like Bloglovin or in the blogrolls of other bloggers, but if you see an address that is unfamiliar it is worth having a look and checking it isn't a splog.
If you set your feed to short, it's also helpful to make sure you have a mobile device template enabled on your blog. This is also simple to do through Blogger. You just go to 'templates' and enable a mobile template. It makes it easier for people to read your blog on a mobile device, so it's well worth doing in any case.
I hope this post is helpful. I'm not a technical wizard by any means so if I can do this, anyone can.
Special apologies to Tsunimee/Liloo who is going to curse me for encouraging people to set their feeds to short. You don't want your favourite blogs deleted though!