For blogs which are published as Public, Blogger provides the option to publish a blog feed - and within that option, what size feed to publish.
- Until Jump Break
When a blog is indexed using the sitemap - and not using the main page, or links from other blogs and websites - the proper feed type will have a major effect on blog indexing. Selecting anything other than "Full" will limit the amount of blog content - and prevent the search engines from indexing the complete blog posts.
(Update 2014/11): This may not be the case, with all blogs using dedicated sitemaps, automatically generated - instead of feed based sitemaps.
Just as indexing of the main page, when you use "Jump Break", affects indexing, so will anything other than "Full" prevent the search engines from accessing the complete blog posts. If your blog is new, you won't have a lot of links from readers. If you select "Short" or "Until Jump Break", indexing of the blog may take longer than "2-3 weeks".
Just because you enable the blog posts newsfeed, to encourage search engine indexing, you may not want to publish comments feeds. The "Custom" selection allows you to separately enable / select feed type for "Blog Posts", "Blog Comment", and "Per-Post Comment" feeds.
The feed size will have a major effect upon re indexing of the blog following a URL change - either a BlogSpot rename, or a custom domain publishing. If you setup a robust sitemap complement, you'll get much better results when the blog publishes a Full feed.
On the other hand, if you publicise the blog using email, and select "Full", you'll want to limit the number of posts in the feed. This will be especially true for photo blogs, and for blogs with large posts.