  Making all data for any observation or experiment openly available is a
defining feature of empirical science (e.g., nullius in verba, the motto of the
Royal Society). It enhances transparency, reproducibility, and societal trust.
While embraced in spirit by many, in practice open data sharing remains the
exception in contemporary systems neuroscience. Here, we take stock of the
Allen Brain Observatory, an effort to share data and metadata associated with
surveys of neuronal activity in the visual system of laboratory mice. The data
from these surveys have been used to produce new discoveries, to validate
computational algorithms, and as a benchmark for comparison with other data,
resulting in over 100 publications and preprints to date. We distill some of
the lessons learned about open surveys and data reuse, including remaining
barriers to data sharing and what might be done to address these.
