- Most residents in Berlin (and in Germany for that matter) rent their apartments.
- There's a fairly good supply of newly built homes. It's still not enough to absorb the population growth, but it's much better than in many German cities.
People complain because they can see the downside of this influx of tech workers very clearly, while the benefits aren't obvious, at least not yet. Rents have doubled in some areas. Government offices are understaffed. So are kindergartens, schools, ...
While the government is partly to blame, a lot of startups haven taken advantage of Berlin's situation in questionable ways. The time where you could hire cheap developers is definitely over, but it's still very common to underpay and abuse people in non-engineering positions, who very often are interns and freelancers.
Kreuzberg is maybe too emblematic and Google is a scapegoat here, but I can understand the resentment against tech incubators.