One thing that i am fully sure is Google does not like inorganic type of any activity. So my opinion is not to spend money on these services rather be active in social media.
@Nathan 229255 wrote:
Some marketers feel that the Google Panda crackdown on link farms has hurt the effectiveness of article marketing, as well.
Whether or not that’s true, Google’s Matt Cutt hasn’t been shy about his feelings on the topic: “Honestly, I’m not a huge fan of article marketing … Typically the sorts of sites that just republish these articles are not the highest quality sites.”
There’s more: Check out the full article here.