Sharing data is encouraged by major funding agencies, and many journals require it as a prerequisite for publication. The NSF specifically states:
Investigators are expected to share with other researchers, at no more than incremental cost and within a reasonable time, the primary data, samples, physical collections and other supporting materials created or gathered in the course of work under NSF grants. Grantees are expected to encourage and facilitate such sharing.
In addition to funder requirements, data sharing is important because it can establish priority, lead to a broader impact for your research, and facilitate advances in science.
