SEO. But now this could not be happen.
As today early morning, Head of Google search spam team "Matt Cutts" had announced on a twitter post that Google has taken action on “a large guest blog network.” With this statement Matt Cutts warned the webmaster and bloggers, not to spam the SEO term with Guest Blogging. SEO community or a group of blogger, who do guest blogging for link building purposes is strictly not allowed from Google spam team.
Blogger who have already done the guest blogging in a large quantity will have some impacts on the Google search rank by the new Google Algorithm.
Today we took action on a large guest blog network. A reminder about the spam risks of guest blogging: http://t.co/rc9O82fjfn
— Matt Cutts (@mattcutts) March 19, 2014
Matt didn't point out the specify the which networks has been effected, but make sure that, those who participated in the unnamed guest blog network will soon see an unnatural link notification in Google Webmaster Tools. This will surely drop the page rank and also a site rank on Google search. Google will continue to target guest blog networks and other link networks in the near future.
The things will be different for those networks which have multiple author blogs, and Google new algorithm will not impacts on these blogs. As this is specially for those blogs and site who rely on guest blogging. Matt have specified there link-building strategy as a Spam technique, and also warned a bloggers not to take a guest blogging unless you are willing to vouch for someone personally or know them well.
Check the video of Matt Cutts on What Google take action on spammy guest blogging.