Upto my knowledge it is better to hire a qualified link building expert than choosing some seo services. Nowadays all seo services are outsourcing their work to others and you won't get the quality you expect.
My company is making a series of plugins that allow for quick setup of common solutions such as ecommerce, directory, search, data grid, tag-based template plugin for detail/category/list view, payment gateway, etc.
One of the features on our roadmap is a series of features that force a user to submit 2 or more blog postings with 8+ keywords which connect to the product or directory listing. The blog postings must be external domains. So for a product catalog or business directory this would create as many link backs on more than 2 externally hosted domains creating a healthy and partly automated SEO feature-set.
I wanted to learn more about how others were coding similar features.
If you mean buying links, know this, any links sold in public, ie where there is a price list and a web site and the process is automated, will be bad on the long run. google will find out and ban the network. Having said that many companies run their own private networks and those are hard to find and more expensive. For example my web development company when we have free unused time creates web sites purely for seo and we use that for our clients.
Yes I fully agree on how to use linkbacks (or how to not use them). As I mentioned in an earlier post a linkback should include an entire blog posting and various related tags.
What I should have also mentioned was the reference to Google's "Hummingbird" Algorithm. From my understanding is Google has a grammar dictionary that checks several words around a link for sentence structure in various languages as well as related TAGS that match meta tags as well as multiple tags listed in a specific area of a page. Obviously there is much more to this.
I am wanting to learn of cutting edge pay-per-use services that have adopted the Google "Hummingbird" Algorithm.
My initial post left me open like a bear trap with fresh warm bloody meat :-)