However, I have the feeling that this is not the main problem encountered by startup employees when they join Google. True, the technology gap can delay product improvements and releases temporarily, but we can expect developers from successful startups to have the right mindset to juggle among many various technologies, from the most basic to the most advanced ones. For a good developer, it must be much less difficult to adapt himself to a new technology than to such a special company in itself.

Let me explicit my point of view. For "normal" people, the recruitment process at Google is very specific. Not only coding and problem solving aptitudes are judged, but also the personality of the hire, in particular whether he would fit in the unique Google mindset. Actually, this is probably the main criterion to pick the right hire today, since Google must have way too many good developers knocking at its door than it will ever need. Yet, people coming from startups are integrated in the company "as is", and since they don't go through this personality-sorting process, they might be bad fits for a career in Google.

Moreover, beyond the fact that these people might be good Googlers or not, the shock for them is probably much more important than for new hires fresh from university. Indeed, Google is organized like a university campus, so that graduates can feel literally at home when they join the company. Nothing that could be more different from a startup, where many employees had to do some harsh sacrifices (in terms of salary, work/life balance, etc).

Last but not least, by joining a big company, startup employees enter the arena of company politics. When the startup was independent and relatively small, everybody could focus on the success of company products. Now, they have to go through the hierarchy overhead (although the hierarchy has the reputation to be quite flat at Google), and even to fight to get resources.

The difference in company culture when a big established company acquires a startup is something quite usual, which happens also to other giants like Microsoft, IBM or Cisco. However, this difference seems to be even more important with a company like Google that valuates so highly its own culture. Maybe this difficulty to integrate properly startups with different cultures is the big drawback of a strategy that works so well to attract the top graduates in computer science. But who cares, as long as the 20% projects emerge...