An under-rated and powerful feature of IBO is the SEO/ranking potential it offers...and with every addition, like the latest IBO answers, the potential increases exponentially. Posting and interlinking keyword-rich content on IBO is crawled rapidly by search engines as IBO has built a long and strong reputation with them.
E.g. Publish a PR and structure your PR to target a keyword/s.
Link to this PR from within other IBO facilities like IBOwall, IBOquestions, etc and ads. Posting later on the Wall and linking to your existing PR is also a means of again bringing your PR to attention and generating clicks and links to it. Do the same from other sources like social media, blog posts, forum comments, etc. All these links should target the same keyword.
In my experience this makes your PR quickly visible to the search engines (best I ever got was #1 in less than an hour once) and gives solid ranking very quickly. I have proven this over and over with lower competition keywords, and I can tell you that once ranked, they stick...even months or years later with no further attention. I can not tell you how effective it is for competitive keywords, but the principle certainly stands.
This idea can be taken further and added to over time which then can start to approximate something like a PBN (private blog network) with the attendant SEO benefits. The more you do of this, the more you solidify your spot in the rankings.
IBO can be used to really "cement" your link at the top of Google...I don't know of another free site with this potential.