[jedberg]

4. (Which is related to 2) Screening college graduates. By releasing "toy" versions of their stuff, they get professors and students using their tools for projects, so when they go to interview with Google, Google already has some data on whether they are using the tools well, and it drives those kids towards google so they can work on "the real thing". It's a great strategy.

[nazka]

Plus 5. Devs learn to use their tool. So when they hire the bests devs (hopefully) elsewhere, they already know how to use their tool without requiring any training time.