Some things people should consider before making their data freely downloadable. Many of these may not apply to you, but they're general considerations. In some cases these are things that should be decided before data are ever collected.
- Are the data truly yours? Does your institution have some claim to the raw data, or to the analysis? Do you have co-authors who also have a claim to the data? Do you have permission from all parties to make this available? Can you document this?
- Is there anything confidential in the data?
- Is there anything copyrighted in the data? Are there other potential legal concerns about making it available? If you have modified or analyzed the data using software, is the download compatible with the software license?
- If humans were involved in any way, is their information anonymized? Did they give permission to make their data available, even in aggregate? Did your institutional review board approve this part of the project? Do you have clear documentation showing this?
- Are you willing and able to maintain the data? Will it be on a site that you control and will control for a period of time? If not, who controls it, and are they willing and able to continue to make it available? What is a reasonable time for the data to remain available -- two years? Five? Twenty?
For many studies, 1-4 may not apply, but 5 is something people don't seem to think about very much. Far too often, individual researchers stick their data, or supplementary information or whatever, up on their institutional web sites, and then two years later their IT people do some reorganization and all the links are broken; or the people move to another institution and their pages are all deleted; or a bug hits and no one notices. Or they put the data up on their personal pages, and then GeoCities is bought by Yahoo! and gets shut down in their country. The web five years ago was a very different place from today, and it will be very different in another five years.
One option is Dryad, which promises to store researcher data; see their claims here. I have no experience with them other than downloading data, but the concept seems good.