In recent months the issues around guest blogging have changed considerably, and the advent of the #hummingbirdupdate have made these issues more important to get right.
So lets just explain the Humming bird issue a bit, then you will have a better insight into what I am trying to say. Open this infographic in a seperate window / browser and go over it briefly.
Note in the sections labeled SOLUTIONS and PRESUMPTIONS the issue of quality and keywords are mentioned and this is of extreme importance, as you want your guest blogger to supply high quality, unique content that is written specifically for your site if you are the site owner.
On the other hand this implies by default that if you are going to be guest blogging for somebody else, your content should be written with the host sites audience in mind, and that you should not be regurgitating stuff that you have plastered all over the web in as many places as you can get your words to be displayed.
These issues are also very relevant to your authorship value and add a great deal of high quality SEOVI (Search Engine Optimisation Value Indicators) to all your related work. The new Humming bird algorithm looks at the author quality and examines other posts and articles that have been written by the same author and looks for rehashed work, or duplicate posts in many different locations. The big G machine has ways and means of detecting these things, and evaluates your work accordingly. If you write the same old stuff again and again in different platforms Google will begin to see you as a spammer, and if you are not careful your work will begin to be devalued in many different ways, as you will acquire the negative points that go along with spamming. These negative points may not be very significant at first, but as they slowly begin to accumulate, and the pattern of regurgitating the same work over and over again emerges in multiple cases you will soon find your work dropping out of the SERP's (Search Engine Results Pages) and you will be scratching your pip and saying to your self "what do I need to do to rank better"
The solution is simple, but you will not get it because you will not be thinking of yourself as a "SPAMMER" Always consider where else you have written an article on the same subject and try to quote that article in your work instead of rehashing the work. When guest blogging this can be difficult, but the new humming bird algorithm is the issue to consider, as humming bird likes these kinds of referrals, and uses them to build your author value and add the necessary SEOVI (Search Engine Optimisation Value Indicators) to a variety of areas including for the publisher (rel = publisher) the author (rel = author) and the content meaning identification factors. So if you are a blog owner and have others posting guest articles consider these factors, and if you are guest blogging for others write them a short email discussing this and asking for the blog owners opinion.
This request for clarity on cross linking and related issues will put you as a guest blogger in a different light with the publisher where your post will be published as a guest post. Some may at first find this offensive as it is counter to the past rules of guest blogging where the blog owner did not want you to link out all over the place as this would perhaps lead the reader astray. But the SEOVI (Search Engine Optimisation Value Indicators) associated with this behavior may well be worth it as the impact on the SERP's (Search Engine Optimisation Pages) will be significant.
Like I said in the first line of this post... this is a lot bigger than you think.
With Humming bird in the picture guest blogging is an awful lot more important than it ever was, and the quality of the work is so much more important for your author value. The SEOVI associated with guest blogging is tremendous, and so is the associated punishment of negative values when you do sloppy work and rehash what you have already written else where.
Guest blogging has just got so much more complicated and we need to get to grips with the true impacts of the humming bird algorithm. As Google gathers more data and more people realise the value of the HTML 5 meta tags of rel = me, rel = author and rel = publisher these things will become clearer and those who take the time to use them will be well rewarded, as those who abuse them will be punished.
My personal opinion is that you had better ensure that you have done the G+ author thing and get to grips with understanding the many issues around G+ pages and publisher rights as viewed by Google. those who do not do this will soon be slipping up on their marketing when their SERP's (Search Engine Results Pages) start to be less impressive than they would like.
See this article by Gina Fiedel for a different perspective.