Earlier quoted context omitted.
The oatmeal wrote about it: | Google's new fleet was intentionally designed to look adorable... By turning self-driving cars into an adorable Skynet Marshmallow Bumper Bots, Google hopes to spiritually disarm other drivers. I also suspect the cuteness is used to quell some of the road rage that might emerge from being stuck behind one of these things. They're intended as moderate-distance couriers, not open-road warr…
Is the 25mph limit a US thing? In the UK the normal minimum (aside from select residential zones where the neighbours complain) is 30mph. Many people would be very annoyed to sit behind a car doing 5 below the speed limit.
I imagine they did 25mph because its slow enough to appease representatives in letting them put the car on the road. Nobody with the ability to actually make this happen is rational or knowledgeable about this, and will behave like psychotic monkeys when confronted with autos, so Google is using every trick in the book to make these look innocent, including Grandma grade speed limits.