I don't think Google Ventures's role is particularly relevant. Companies should be aware of what data they are providing Google when making use of Google services. Google doesn't need to have insider information to have a wealth of information about Uber trips: the number of trips, when they most frequently occur, duration and miles covered, what cities are most popular, what are the popular starting and ending points. All of these data can be mined from just watching Uber's use of the Google Maps API. It may not be contractually permitted, but the data are there for Google to use.
Through a paranoid lens, Google APIs are corporate espionage you sign up for. Since Google is a valuable and entrenched service provider, they can get away with it. What I could see companies doing in return is attempting to obscure their API usage by fabricating requests. For example, Uber could break the correspondence between API requests and trips by sending requests that look authentic but don't correspond to any actual trips. This kind of corporate information warfare sounds like something out of a William Gibson novel, but it certainly feels present and real when you look at Google's relationships.