Paid backlink building is in no way good for business. SEO Roundtable speaks on Google's Matt Cutts discussing the negatives of paid links. On a paid backlink SEO site, they mention the following nonsense:
"Need Help with Your Link Building?
Although our Link Wizard makes it easy to build an effective and sustainable link portfolio, we also have an internal SEO team that will build your links for you FOR FREE if you purchase at least $100 in credits.
Just create a new link advertiser account or log into your existing account.
Then, click the red “Free Link Placement” graphic on your dashboard home to get started."
Related: Earn SEO respect by building links naturally
How could they profess something to be free, yet, ask people to purchase at least $100 in credits? If something is free, it's free, right? This sounds like a scam.
If you engage in purchasing paid backlinks to inflate your SEO, truth is, your site will be excluded sooner or later from Google search results and other search engines. No one wants to be associated with a site that inflates themselves dishonestly.
Recently, a paid SEO backlink company recently sent out spam e-mails to affiliates and former affiliates about backlink building news. The illegal paid backlink company has no "about" section on their website nor a phone number to contact their offices for more information. If any paid SEO backlink building company contacts you for any reason, ignore them, label their mail as "spam," unsubscribe if you subscribed in the past, and blacklist their name and e-mail address in your contacts folder. Quality backlinks are built naturally when you write good content and people link to it. Natural backlinks are also built when you share content on social networks. You can use free 3rd party automated content sharing applications to autoshare content to social networks. This is considered a "White hat SEO link building strategy," as search engines are A-ok with that.
As long as you're not in any form, shape, or fashion paying for backlinks, natural link building is great. If anything, you can build quality backlinks by creating documents with links in the body of the document to point ot pages or your URL homepage and submit those documents to sites like DocStoc.com or Scribd.com. Submitting naturally written documents with links pointing to your blog or website and submitting frequently to those document sharing sites are White hat SEO link building strategies and search engines will reward you with free traffic long term. Just as long as you keep submitting quality written documents to those sites and include hyperlinks in the body of the document to pages on your blog or website, you'll always be good on improving SEO and increasing quality backlinks.
Update: As of December 2015, DocStoc has been shut down for business. Their domain name looks as if it's possibly up for grabs.
Los Angeles Times
Scribd remains king on document sharing. Be mindful to offer value in the body of all submitted documents so you keep people coming back for more.