That's not to say the Play store doesn't drive me to distraction sometimes... I recently had to look at over a dozen flashlight apps to find one or two that weren't spamming me with ads and looking at my personal information.
PS: Here's the Mac App Store 'Facebook' search: http://i.imgur.com/8o8mveb.png
About your screenshot - maybe I'm missing something, but where in the results is the official Facebook app? Do they hide already installed apps?
I can't speak for others, but for me the Microsoft dominance has been a pain until I started mastering Linux. I am very happy if it is confirmed that HN actively removes links about Microsoft, just as a cold personal feeling of street justice. So it's not HN, it's the crowd of geeks.
On the other hand I don't see why HN would do that. Sounds like a loss of time and a PR risk. Maybe your content was average quality, maybe it wasn't cool enough, maybe it contained inappropriate contents. Please refer to the guidelines [1] to check whether your content had a chance to survive.