We use MySQL in a variety of ways both internal to Dewpoint and among our customers:
1. It is the backend utility database for a variety of tools such as Jira, Bugzilla, NoSQL tools, etc.
2. It is an application database for some web based applications.
3. It is a caching database used at local customer sites for larger applications.
4. It is a prototyping database during initial phases of development before deploying on a more expensive RDBMS such as Oracle or SQL Server.
MySQL represents a reliable and simple database that supports standard SQL with good tools and good integration points.