"Information wants to be free." So said Stewart Brand at the first Hackers Conference in 1984. If you take a few precautions, you can share your data with the world by giving SQL access to any Internet user. Both of the authors of this book have been allowing public access to their SQL machines for years, with few problems. Generally we find that a hundred local, "trusted" users cause more trouble than hundreds of thousands of external users.
Even if you can't share your data with the world, there's a chance that you can share more of it with more people in your organization, or with partners in other organizations. The more widely you share your data the more work you have to do to keep it safe and protect the system against poorly written queries.
If you allow SQL-level access to your database, people can develop their own interfaces or reuse general-purpose query-building applications.