There is the one where the company wants to reward top performers. I think this one is most common, and I have never worked at a company that doesn't so some form of bonus budgeting that tries to capture a group of employees who are performing well and give them a bonus. The budget itself dictates how many employees can fit into that group, so ultimately what happens is a natural bell curve of the biggest rewards going to the perceived top performers, as agreed upon by managers usually at the organization level.
The other more insidious stack ranking involves a punitive element, whereby a group must necessarily be singled out for performance improvement reasons. This is the type of thing where managers, no matter what the team members actually accomplished, have to put someone on a performance improvement plan or start performance managing them to "get them up the bar" because someone naturally has to fall into the "bottom performer" bucket of stack ranking.
I think the former is common and pretty unavoidable unless a company has an unusually large bonus budget pool available. The latter approach is what causes problems with companies, because all of a sudden team mates become competitors and cultures can go downhill rapidly. Think Amazon, Microsoft under Ballmer, and GE under Walsh.
It's kind of interesting how many companies who are doing the former bonus budget pooling eventually get seduced into doing the latter and destroying their culture.