Yes - backlinks DO help your earnings go up because they increase your page views.
Especially important are "dofollow" backlinks, and those are important because those are the kind of backlinks that Google uses to calculate and decide where in their search engine results pages that your hubs should go for the search terms that someone would use to find your hubs on the web.
Simply put - you won't make money if nobody sees your hubs, and backlinks ensure that the search engines know your hubs exist, and that they are good enough to be listed in search results.
Social networking sites are really easy to use for backlinks, but those sites are NOT the "dofollow" backlinks.
They are still well worth your time though, and I generally get loads of views from Facebook every week. Twitter and Tumblr are other good social network sites, and some folks get a lot of traffic from those, but I just don't tend to spend much time on either of those two.
Google + is another good social network site to backlink to, and I do get some views from there as well.
Here is a short list of "dofollow" backlink sites that I use:
Article Blast and,
...and now I'm writing some on Xobba Tribune, where I write some original articles, and also include a very related backlink to either here, or my articles on Info Barrel.
Excertz is another good site you can join to write articles while linking to your work here.
For basic backlinking I suggest that you use either Google Chrome, or Mozilla Firefox as a browser, and with either browser you can download and add the AddThis extension..which is easily customizable for you to backlink on your social networks and bookmarking sites of choice.
If something isn't available as an option with the AddThis extension, then I always add the site not available as a bookmark on my browser so that it is easy to go there and create a backlink.