It seems like a pretty meritocratic way to earn a bigger pay raise than you'd normally get.
It's also a common strategy for someone in an organization to make a big vertical leap or move across the organization in a way that would be nearly impossible internally. Basically, an infrastructure engineer leaves and comes back as a VP of Product for social wizardry.
2. Startup does stuff that Google wants
3. Google acquires startup, Googler is back at Google
4. ???
5. Profit!!