Facebook posts made though 3rd party APIs like Hootsuite attract less than 1/4 the engagement of posts made directly

"It’s been a general consensus in the EdgeRank community that 3rd party APIs (this simple list provides examples of potential 3rd Party APIs) are punished in Facebook’s EdgeRank algorithm. We ran a study across our entire data set to provide evidence that our hypothesis is true. The result of our study was quite eye opening. Using a 3rd party API to update your Facebook Page decreases your likelihood of engagement per fan (on average) by about 80%.
We ran our analysis on 1,000,000+ Updates on 50,000+ Pages that influence over 1,000,000,000+ Fans. We took each individual post and analyzed the engagement (comment & likes) along with how many fans the Page had at the moment of updating. We then analyzed Facebook vs The Top 10 Other APIs (based on our sample size). We did a weighted average for the 3rd Party APIs, which resulted in 0.22% engagement. The result is a percentage that represents engagement per fan per post (on weighted average, of our Top 10 3rd Party API). Our sample size ranged per API, although we cut it off at the Top 10 APIs outside of Facebook."

Source:  Data from EdgeRank Checker, reported on their blog, 6th September 2011