So there are several interesting hiring related phenomenon I've seen at various companies. I think some of the most exaggerated hiring behavior will emerge at "flat" companies with yearly bonuses based (partially) from the data gathered during peer feedback.
Here's a description of one category of emergent behavior I noticed when the programmers have nearly free reign to run the hiring process and who will ultimately get hired:
Want a good bonus? Never hire new competition!
You would think the programmers doing the hiring would always be fair and unbiased in their assessments of each candidate's abilities, right? And they would, of course, always optimize for adding value to the company by making good hires. The company programmers involved in the process would choose good candidates for each opening, irrespective of politics, or concerns over their future positions or bonuses, etc.
In practice, I think especially at companies with massive yearly bonuses, the company's programmers will band together unofficially and make it practically impossible for potential competition to enter the company, make waves, and possibly eclipse the old guard. We have a classic conflict of interest situation here. This tendency to embargo your competition is especially effective when hiring specialists, such as graphics programmers, although I've seen it happen regardless of specialty.
At one well-known company, I watched around a dozen experienced graphics programmers get rejected in our interview process. Each time, without exception it was a NO HIRE, even though we were in dire need of graphics programmers. A few of the names were pretty well known in graphics circles, so my jaw dropped after several of these NO HIRE interviews.
I was involved in some of these interviews. Almost every time, these candidates would do sometimes incredible things during the whiteboard interview, but somehow one or two graphics programmers would always find some other reason to be thumbs down. (I didn't say anything at the time, because I was afraid doing so would have made enemies and hurt my career at this company. I was basically incentivized to say nothing by the peer feedback based bonus system.)
Eventually, upper management quietly noticed that irrespective of our company's dire need of graphics engineers, we weren't hiring them anyway. This company had a major upcoming threat to its primary profit generating product looming in its future, and the counter to this competitive threat involved some very specialized graphics engineering. The CEO had to step in and basically just subvert the entire completely broken hiring process and just start hiring graphics contractors almost sight unseen.
Unfortunately, these graphics contractors had virtually no path to full-time employment, so they got treated like 3rd class citizens at best and all were eventually pushed out. (Sometimes years later, even after delivering massive amounts of value to some teams.)
Anyhow, how do I know all this stuff? At this particular company, I somehow fell through the cracks and was interviewed and hired as a generalist programmer, not a graphics specialists. Eventually, the old graphics guard basically got lazy and shied away from the company's toughest graphics problems (or actually shipping anything involving new graphics code), but somebody had to do this "dirty" graphics work. The non-graphics programmers figured things out and started sending graphics work my way, and I started asking myself "why are we not hiring any graphics programmers?!"
Unfortunately I'm terrible at saying "no" to requests for help, so this resulted in a lot of work.
Turns out, that refined, "fair" hiring machine that management was so proud of was a total joke.