This is why big companies get slow and bloated. Behavior like this only happens when people are in it for the money and don't really care about what they're building.
From what I have read, Google doesn't operate this way. My understanding is they don't keep everyone from an acquisition. While this seems a bit rude fire someone or make talented engineers re-apply for their own job, it does mean the people they do keep become Google engineers rather than 2 year indentured servants who have no incentive to join the company culture.
Back in the day (circa 1996 with my experience), MSFT made employees from acquisitions re-apply for their jobs and go through the full interview process.
