(The Basics: What a Blog Network Is) A blog network is a consortium of websites, often numbering into the hundreds, and even thousands, that, over the course of building authority for each site in the network, utilizes that authority (generally measured and marketed by PR [PageRank]) as a means by which to make money by way of offering ? for a cost ? a post on some or all of the sites in the network. The net effect being increased search engine rankings for the keywords one uses in the posts, on the sites in the blog network, for the website or webpage to which the site in the network links. The Good: Private Blog networks offer ?permanent? backlink placements: One of the pitfalls of SEO, in any form, is what is generally referred to as the ?stick rate? of the links one builds or has built for their Web property. When one builds a backlink on any webpage that they do not own, there is no guarantee that the link will ?stick? (i.e. be around) for any length of time. Therefore, the more certain one can be that the link one wants to post not only gets posted, but is present on a given webpage indefinitely, the more valuable that link is to the overall portfolio of links one has built for any given website. Since search engines assess aged backlinks more positively as they age (thereby increasing their strength over time, especially if particularly relevant), the importance of ?permanent? backlinks is paramount in long-term SERPs success and ranking stability. Private blog networks often offer backlink opportunities that simply do not exist with any other backlink types. For example, many ?Buy? keywords (e.g. buy blue widgets), keywords almost universally considered to be ?spammy? (e.g. various boner pills); and, exceedingly niche topics already dominated by big brands (e.g. trash bags, table lamps, etc.). In other words, private blog networks provide ranking opportunities for sites that are otherwise nearly, if not completely, impossible to rank well in SERPs by more traditional backlinking means. Private blog network links are contextual links, thereby providing ranking opportunities not only for the hot-linked keyword, but also for any number of relevant keyword combinations, as dictated by the content surrounding the link, and the content of the webpage to which the link ? itself ? is pointed. (This is admittedly rather complicated ? have a question? Just ask.) The Bad: Most private blog networks suck and for the most there is no way to know if one does until ? and unless ? the network provider/administrator is willing to provide a report. There are multiple reasons why most BN?s suck, but the most salient of which is that the PR (again: PageRank) of most sites in most networks are what we (me and mine) refer to as ?unstable?. Unstable PR refers to HOW the site in the network has acquired the PR that it has. For example, many blog networks employ reciprocal linking schemes that prop-up the PR of the network as a whole. To illustrate this, it helps by thinking of each site in the network as a link in a greater chain: when one falls, so go the others if for no other reason that the weakest link in the chain. Many private blog network sites also have PR that is, for lack of a better word, inexplicable: these are sites in the network that have real and true PageRank, but you ? as the consumer ? have no reasonable means to perform due diligence as to how that site acquired that PR. While correlation does not equal causation, what I can say with confidence, and am equally confident in passing on to you guys, is that when ? with all of the tools that are out there ? one cannot figure out in a completely transparent way HOW a website has gotten the PR that it has, that PR is transitory at best; and, is 99% of the time, going to fall with the next Google PR update. The Ugly: Google is aware of the slight majority of private blog networks that exist, but keeps them indexed ? and in some instances ranks them highly on purpose ? so as to acquire data to use against sites that are ?violating? their TOS; and, to acquire data to better help them define footprints so as to automate penalties, link devaluations and de-indexations. What does this mean for you? In a word, ALL blog networks are ?dangerous?, insofar as one values the LONG-TERM success of their Web property. Further, Google has resources that no one else has: there is not a single blog network in existence that will not (eventually) be found-out by Google. In Conclusion: Private blog networks certainly have their place in the current SEO environment. But, this is not to say that blog networks always will. As always: diversify your website?s backlink portfolio. If you are going to buy placements on private networks, realize, and take to heart, that these links are not in actuality ?permanent?; but are, the most effective means to rank a Web property in the short- and medium terms.