What is the purpose of getting +1's?The search engines most likely have no special processing, for social action like +1s and Likes - but indexing of content will include social shared content, and notifications of +1s and Likes, from FaceBook and Google+.
A blog post, shared or given a +1, will become part of a Google+ stream - similar to a Blogger blog comment, that is Google+ hosted. The search engines index Google+ stream posts, as they index blogs. There will be similar action from FaceBook content.
A Google+ stream post will include a snippet of the blog post opening paragraph, plus a link to the post.
An indexed stream post will link to the blog post - and provide search reputation.
An indexed stream post will then provide a link to the blog post - and the stream post, when indexed, will lead to indexing of the blog post.
The more shares, and +1s / Likes, received by any blog post, the more reputation from the search engines - because of indexing of Google+ streams. And as a stream post replicates through the streams of Followers, it becomes more visible to the search engines - and one stream post, and blog post, receives still more reputation.
An example stream post, that started with a blog post being shared.
Here's a stream post, from my share of my post Search Engine Reputation, And Vanity Domains, into my Google+ collection, "RBS". Look at the post to the right.
A Google+ stream post, which started with my blog post, shared to Google+.
See what gets shared?
The Google+ post content:
Some #Blogger blog owners are intent on publishing a blog to a custom domain, using a top level domain that relates to the blog subject. They do this, hoping to have a unique blog name.
They may overlook the idea that Blogger blogs benefit from well written and unique content, as much as from a shiny and unique URL.
A photo from the blog post, captioning a link to the blog post:
The blog post title, captioning a link to the blog post:
The blog URL, captioning a link to the blog post:
The blog post meta search description:
Blog owners who develop a reputation strategy based on the URL may find that won't help as they hoped. Learn why.
Some or all of that shows in the Notification window and / or peoples streams, when someone +1s, or reshares, that stream post.
The blog post title, and meta search description, are part of a properly constructed post - and properly sized to fit into a Google+ stream column.
This content (with 3 captioned links), when indexed by a search engine, contributes to search engine reputation for the blog post. And as the stream post ripples through the streams of the Followers - and the Followers of the Followers - it contributes more reputation.
A share or Like / +1 of a #Blogger blog post, in a social networking system like FaceBook / Google+, does not contribute directly to a search engine "Share", "Like", or "+1" database - but it does contribute, indirectly, to search reputation for the post in question.